gitattributes

package: git-core

title: gitattributes(5)

summary: Defining attributes per path

text:
# gitattributes(5)

## NAME
gitattributes - Defining attributes per path

## SYNOPSIS
$GIT_DIR/info/attributes, .gitattributes

## DESCRIPTION
A gitattributes file is a simple text file that gives attributes to pathnames.

Each line in gitattributes file is of form:

```
pattern attr1 attr2 ...
```

That is, a pattern followed by an attributes list, separated by whitespaces. Leading and trailing whitespaces are ignored. Lines that begin with # are ignored. Patterns that begin with a double quote are quoted in C style. When the pattern matches the path in question, the attributes listed on the line are given to the path.

Each attribute can be in one of these states for a given path:

Set

The path has the attribute with special value "true"; this is specified by listing only the name of the attribute in the attribute list.

Unset

The path has the attribute with special value "false"; this is specified by listing the name of the attribute prefixed with a dash - in the attribute list.

Set to a value

The path has the attribute with specified string value; this is specified by listing the name of the attribute followed by an equal sign = and its value in the attribute list.

Unspecified

No pattern matches the path, and nothing says if the path has or does not have the attribute, the attribute for the path is said to be Unspecified.

When more than one pattern matches the path, a later line overrides an earlier line. This overriding is done per attribute.

The rules by which the pattern matches paths are the same as in .gitignore files (see gitignore(5)), with a few exceptions:

•negative patterns are forbidden

•patterns that match a directory do not recursively match paths inside that directory (so using the trailing-slash path/ syntax is pointless in an attributes file; use path/** instead)

When deciding what attributes are assigned to a path, Git consults $GIT_DIR/info/attributes file (which has the highest precedence), .gitattributes file in the same directory as the path in question, and its parent directories up to the toplevel of the work tree (the further the directory that contains .gitattributes is from the path in question, the lower its precedence). Finally global and system-wide files are considered (they have the lowest precedence).

When the .gitattributes file is missing from the work tree, the path in the index is used as a fall-back. During checkout process, .gitattributes in the index is used and then the file in the working tree is used as a fall-back.

If you wish to affect only a single repository (i.e., to assign attributes to files that are particular to one user’s workflow for that repository), then attributes should be placed in the $GIT_DIR/info/attributes file. Attributes which should be version-controlled and distributed to other repositories (i.e., attributes of interest to all users) should go into .gitattributes files. Attributes that should affect all repositories for a single user should be placed in a file specified by the core.attributesFile configuration option (see git-config(1)). Its default value is $XDG_CONFIG_HOME/git/attributes. If $XDG_CONFIG_HOME is either not set or empty, $HOME/.config/git/attributes is used instead. Attributes for all users on a system should be placed in the $(prefix)/etc/gitattributes file.

Sometimes you would need to override a setting of an attribute for a path to Unspecified state. This can be done by listing the name of the attribute prefixed with an exclamation point !.

## RESERVED BUILTIN_* ATTRIBUTES
builtin_* is a reserved namespace for builtin attribute values. Any user defined attributes under this namespace will be ignored and trigger a warning.

### builtin_objectmode
This attribute is for filtering files by their file bit modes (40000, 120000, 160000, 100755, 100644). e.g. :(attr:builtin_objectmode=160000). You may also check these values with git check-attr builtin_objectmode -- <file>. If the object is not in the index git check-attr --cached will return unspecified.

## EFFECTS
Certain operations by Git can be influenced by assigning particular attributes to a path. Currently, the following operations are attributes-aware.

### Checking-out and checking-in
These attributes affect how the contents stored in the repository are copied to the working tree files when commands such as git switch, git checkout and git merge run. They also affect how Git stores the contents you prepare in the working tree in the repository upon git add and git commit.

text

This attribute marks the path as a text file, which enables end-of-line conversion: When a matching file is added to the index, the file’s line endings are normalized to LF in the index. Conversely, when the file is copied from the index to the working directory, its line endings may be converted from LF to CRLF depending on the eol attribute, the Git config, and the platform (see explanation of eol below).

Set

Setting the text attribute on a path enables end-of-line conversion on checkin and checkout as described above. Line endings are normalized to LF in the index every time the file is checked in, even if the file was previously added to Git with CRLF line endings.

Unset

Unsetting the text attribute on a path tells Git not to attempt any end-of-line conversion upon checkin or checkout.

Set to string value "auto"

When text is set to "auto", Git decides by itself whether the file is text or binary. If it is text and the file was not already in Git with CRLF endings, line endings are converted on checkin and checkout as described above. Otherwise, no conversion is done on checkin or checkout.

Unspecified

If the text attribute is unspecified, Git uses the core.autocrlf configuration variable to determine if the file should be converted.

Any other value causes Git to act as if text has been left unspecified.

eol

This attribute marks a path to use a specific line-ending style in the working tree when it is checked out. It has effect only if text or text=auto is set (see above), but specifying eol automatically sets text if text was left unspecified.

Set to string value "crlf"

This setting converts the file’s line endings in the working directory to CRLF when the file is checked out.

Set to string value "lf"

This setting uses the same line endings in the working directory as in the index when the file is checked out.

Unspecified

If the eol attribute is unspecified for a file, its line endings in the working directory are determined by the core.autocrlf or core.eol configuration variable (see the definitions of those options in git-config(1)). If text is set but neither of those variables is, the default is eol=crlf on Windows and eol=lf on all other platforms.

Backwards compatibility with crlf attribute

For backwards compatibility, the crlf attribute is interpreted as follows:

```
crlf            text
-crlf           -text
crlf=input      eol=lf
```

End-of-line conversion

While Git normally leaves file contents alone, it can be configured to normalize line endings to LF in the repository and, optionally, to convert them to CRLF when files are checked out.

If you simply want to have CRLF line endings in your working directory regardless of the repository you are working with, you can set the config variable "core.autocrlf" without using any attributes.

```
[core]

        autocrlf = true
```

This does not force normalization of text files, but does ensure that text files that you introduce to the repository have their line endings normalized to LF when they are added, and that files that are already normalized in the repository stay normalized.

If you want to ensure that text files that any contributor introduces to the repository have their line endings normalized, you can set the text attribute to "auto" for all files.

```
*       text=auto
```

The attributes allow a fine-grained control, how the line endings are converted. Here is an example that will make Git normalize .txt, .vcproj and .sh files, ensure that .vcproj files have CRLF and .sh files have LF in the working directory, and prevent .jpg files from being normalized regardless of their content.

```
*               text=auto
*.txt           text
*.vcproj        text eol=crlf
*.sh            text eol=lf
*.jpg           -text
```

Note When text=auto conversion is enabled in a cross-platform project using push and pull to a central repository the text files containing CRLFs should be normalized.

From a clean working directory:

```
$ echo "* text=auto" >.gitattributes
$ git add --renormalize .
$ git status        # Show files that will be normalized
$ git commit -m "Introduce end-of-line normalization"
```

If any files that should not be normalized show up in git status, unset their text attribute before running git add -u.

```
manual.pdf      -text
```

Conversely, text files that Git does not detect can have normalization enabled manually.

```
weirdchars.txt  text
```

If core.safecrlf is set to "true" or "warn", Git verifies if the conversion is reversible for the current setting of core.autocrlf. For "true", Git rejects irreversible conversions; for "warn", Git only prints a warning but accepts an irreversible conversion. The safety triggers to prevent such a conversion done to the files in the work tree, but there are a few exceptions. Even though...

•git add itself does not touch the files in the work tree, the next checkout would, so the safety triggers;

•git apply to update a text file with a patch does touch the files in the work tree, but the operation is about text files and CRLF conversion is about fixing the line ending inconsistencies, so the safety does not trigger;

•git diff itself does not touch the files in the work tree, it is often run to inspect the changes you intend to next git add. To catch potential problems early, safety triggers.

working-tree-encoding

Git recognizes files encoded in ASCII or one of its supersets (e.g. UTF-8, ISO-8859-1, ...) as text files. Files encoded in certain other encodings (e.g. UTF-16) are interpreted as binary and consequently built-in Git text processing tools (e.g. git diff) as well as most Git web front ends do not visualize the contents of these files by default.

In these cases you can tell Git the encoding of a file in the working directory with the working-tree-encoding attribute. If a file with this attribute is added to Git, then Git re-encodes the content from the specified encoding to UTF-8. Finally, Git stores the UTF-8 encoded content in its internal data structure (called "the index"). On checkout the content is re-encoded back to the specified encoding.

Please note that using the working-tree-encoding attribute may have a number of pitfalls:

•Alternative Git implementations (e.g. JGit or libgit2) and older Git versions (as of March 2018) do not support the working-tree-encoding attribute. If you decide to use the working-tree-encoding attribute in your repository, then it is strongly recommended to ensure that all clients working with the repository support it. For example, Microsoft Visual Studio resources files (*.rc) or PowerShell script files (*.ps1) are sometimes encoded in UTF-16. If you declare *.ps1 as files as UTF-16 and you add foo.ps1 with a working-tree-encoding enabled Git client, then foo.ps1 will be stored as UTF-8 internally. A client without working-tree-encoding support will checkout foo.ps1 as UTF-8 encoded file. This will typically cause trouble for the users of this file.

If a Git client that does not support the working-tree-encoding attribute adds a new file bar.ps1, then bar.ps1 will be stored "as-is" internally (in this example probably as UTF-16). A client with working-tree-encoding support will interpret the internal contents as UTF-8 and try to convert it to UTF-16 on checkout. That operation will fail and cause an error.

•Reencoding content to non-UTF encodings can cause errors as the conversion might not be UTF-8 round trip safe. If you suspect your encoding to not be round trip safe, then add it to core.checkRoundtripEncoding to make Git check the round trip encoding (see git-config(1)). SHIFT-JIS (Japanese character set) is known to have round trip issues with UTF-8 and is checked by default.

•Reencoding content requires resources that might slow down certain Git operations (e.g git checkout or git add).

Use the working-tree-encoding attribute only if you cannot store a file in UTF-8 encoding and if you want Git to be able to process the content as text.

As an example, use the following attributes if your *.ps1 files are UTF-16 encoded with byte order mark (BOM) and you want Git to perform automatic line ending conversion based on your platform.

```
*.ps1           text working-tree-encoding=UTF-16
```

Use the following attributes if your *.ps1 files are UTF-16 little endian encoded without BOM and you want Git to use Windows line endings in the working directory (use UTF-16LE-BOM instead of UTF-16LE if you want UTF-16 little endian with BOM). Please note, it is highly recommended to explicitly define the line endings with eol if the working-tree-encoding attribute is used to avoid ambiguity.

```
*.ps1           text working-tree-encoding=UTF-16LE eol=crlf
```

You can get a list of all available encodings on your platform with the following command:

```
iconv --list
```

If you do not know the encoding of a file, then you can use the file command to guess the encoding:

```
file foo.ps1
```

ident

When the attribute ident is set for a path, Git replaces $Id$ in the blob object with $Id:, followed by the 40-character hexadecimal blob object name, followed by a dollar sign $ upon checkout. Any byte sequence that begins with $Id: and ends with $ in the worktree file is replaced with $Id$ upon check-in.

filter

A filter attribute can be set to a string value that names a filter driver specified in the configuration.

A filter driver consists of a clean command and a smudge command, either of which can be left unspecified. Upon checkout, when the smudge command is specified, the command is fed the blob object from its standard input, and its standard output is used to update the worktree file. Similarly, the clean command is used to convert the contents of worktree file upon checkin. By default these commands process only a single blob and terminate. If a long running process filter is used in place of clean and/or smudge filters, then Git can process all blobs with a single filter command invocation for the entire life of a single Git command, for example git add --all. If a long running process filter is configured then it always takes precedence over a configured single blob filter. See section below for the description of the protocol used to communicate with a process filter.

One use of the content filtering is to massage the content into a shape that is more convenient for the platform, filesystem, and the user to use. For this mode of operation, the key phrase here is "more convenient" and not "turning something unusable into usable". In other words, the intent is that if someone unsets the filter driver definition, or does not have the appropriate filter program, the project should still be usable.

Another use of the content filtering is to store the content that cannot be directly used in the repository (e.g. a UUID that refers to the true content stored outside Git, or an encrypted content) and turn it into a usable form upon checkout (e.g. download the external content, or decrypt the encrypted content).

These two filters behave differently, and by default, a filter is taken as the former, massaging the contents into more convenient shape. A missing filter driver definition in the config, or a filter driver that exits with a non-zero status, is not an error but makes the filter a no-op passthru.

You can declare that a filter turns a content that by itself is unusable into a usable content by setting the filter.<driver>.required configuration variable to true.

Note: Whenever the clean filter is changed, the repo should be renormalized: $ git add --renormalize .

For example, in .gitattributes, you would assign the filter attribute for paths.

```
*.c     filter=indent
```

Then you would define a "filter.indent.clean" and "filter.indent.smudge" configuration in your .git/config to specify a pair of commands to modify the contents of C programs when the source files are checked in ("clean" is run) and checked out (no change is made because the command is "cat").

```
[filter "indent"]

        clean = indent

        smudge = cat
```

For best results, clean should not alter its output further if it is run twice ("clean→clean" should be equivalent to "clean"), and multiple smudge commands should not alter clean's output ("smudge→smudge→clean" should be equivalent to "clean"). See the section on merging below.

The "indent" filter is well-behaved in this regard: it will not modify input that is already correctly indented. In this case, the lack of a smudge filter means that the clean filter must accept its own output without modifying it.

If a filter must succeed in order to make the stored contents usable, you can declare that the filter is required, in the configuration:

```
[filter "crypt"]

        clean = openssl enc ...

        smudge = openssl enc -d ...

        required
```

Sequence "%f" on the filter command line is replaced with the name of the file the filter is working on. A filter might use this in keyword substitution. For example:

```
[filter "p4"]

        clean = git-p4-filter --clean %f

        smudge = git-p4-filter --smudge %f
```

Note that "%f" is the name of the path that is being worked on. Depending on the version that is being filtered, the corresponding file on disk may not exist, or may have different contents. So, smudge and clean commands should not try to access the file on disk, but only act as filters on the content provided to them on standard input.

Long Running Filter Process

If the filter command (a string value) is defined via filter.<driver>.process then Git can process all blobs with a single filter invocation for the entire life of a single Git command. This is achieved by using the long-running process protocol (described in Documentation/technical/long-running-process-protocol.adoc).

When Git encounters the first file that needs to be cleaned or smudged, it starts the filter and performs the handshake. In the handshake, the welcome message sent by Git is "git-filter-client", only version 2 is supported, and the supported capabilities are "clean", "smudge", and "delay".

Afterwards Git sends a list of "key=value" pairs terminated with a flush packet. The list will contain at least the filter command (based on the supported capabilities) and the pathname of the file to filter relative to the repository root. Right after the flush packet Git sends the content split in zero or more pkt-line packets and a flush packet to terminate content. Please note, that the filter must not send any response before it received the content and the final flush packet. Also note that the "value" of a "key=value" pair can contain the "=" character whereas the key would never contain that character.

```
packet:          git> command=smudge
packet:          git> pathname=path/testfile.dat
packet:          git> 0000
packet:          git> CONTENT
packet:          git> 0000
```

The filter is expected to respond with a list of "key=value" pairs terminated with a flush packet. If the filter does not experience problems then the list must contain a "success" status. Right after these packets the filter is expected to send the content in zero or more pkt-line packets and a flush packet at the end. Finally, a second list of "key=value" pairs terminated with a flush packet is expected. The filter can change the status in the second list or keep the status as is with an empty list. Please note that the empty list must be terminated with a flush packet regardless.

```
packet:          git< status=success
packet:          git< 0000
packet:          git< SMUDGED_CONTENT
packet:          git< 0000
packet:          git< 0000  # empty list, keep "status=success" unchanged!
```

If the result content is empty then the filter is expected to respond with a "success" status and a flush packet to signal the empty content.

```
packet:          git< status=success
packet:          git< 0000
packet:          git< 0000  # empty content!
packet:          git< 0000  # empty list, keep "status=success" unchanged!
```

In case the filter cannot or does not want to process the content, it is expected to respond with an "error" status.

```
packet:          git< status=error
packet:          git< 0000
```

If the filter experiences an error during processing, then it can send the status "error" after the content was (partially or completely) sent.

```
packet:          git< status=success
packet:          git< 0000
packet:          git< HALF_WRITTEN_ERRONEOUS_CONTENT
packet:          git< 0000
packet:          git< status=error
packet:          git< 0000
```

In case the filter cannot or does not want to process the content as well as any future content for the lifetime of the Git process, then it is expected to respond with an "abort" status at any point in the protocol.

```
packet:          git< status=abort
packet:          git< 0000
```

Git neither stops nor restarts the filter process in case the "error"/"abort" status is set. However, Git sets its exit code according to the filter.<driver>.required flag, mimicking the behavior of the filter.<driver>.clean / filter.<driver>.smudge mechanism.

If the filter dies during the communication or does not adhere to the protocol then Git will stop the filter process and restart it with the next file that needs to be processed. Depending on the filter.<driver>.required flag Git will interpret that as error.

Delay

If the filter supports the "delay" capability, then Git can send the flag "can-delay" after the filter command and pathname. This flag denotes that the filter can delay filtering the current blob (e.g. to compensate network latencies) by responding with no content but with the status "delayed" and a flush packet.

```
packet:          git> command=smudge
packet:          git> pathname=path/testfile.dat
packet:          git> can-delay=1
packet:          git> 0000
packet:          git> CONTENT
packet:          git> 0000
packet:          git< status=delayed
packet:          git< 0000
```

If the filter supports the "delay" capability then it must support the "list_available_blobs" command. If Git sends this command, then the filter is expected to return a list of pathnames representing blobs that have been delayed earlier and are now available. The list must be terminated with a flush packet followed by a "success" status that is also terminated with a flush packet. If no blobs for the delayed paths are available, yet, then the filter is expected to block the response until at least one blob becomes available. The filter can tell Git that it has no more delayed blobs by sending an empty list. As soon as the filter responds with an empty list, Git stops asking. All blobs that Git has not received at this point are considered missing and will result in an error.

```
packet:          git> command=list_available_blobs
packet:          git> 0000
packet:          git< pathname=path/testfile.dat
packet:          git< pathname=path/otherfile.dat
packet:          git< 0000
packet:          git< status=success
packet:          git< 0000
```

After Git received the pathnames, it will request the corresponding blobs again. These requests contain a pathname and an empty content section. The filter is expected to respond with the smudged content in the usual way as explained above.

```
packet:          git> command=smudge
packet:          git> pathname=path/testfile.dat
packet:          git> 0000
packet:          git> 0000  # empty content!
packet:          git< status=success
packet:          git< 0000
packet:          git< SMUDGED_CONTENT
packet:          git< 0000
packet:          git< 0000  # empty list, keep "status=success" unchanged!
```

Example

A long running filter demo implementation can be found in contrib/long-running-filter/example.pl located in the Git core repository. If you develop your own long running filter process then the GIT_TRACE_PACKET environment variables can be very helpful for debugging (see git(1)).

Please note that you cannot use an existing filter.<driver>.clean or filter.<driver>.smudge command with filter.<driver>.process because the former two use a different inter process communication protocol than the latter one.

Interaction between checkin/checkout attributes

In the check-in codepath, the worktree file is first converted with filter driver (if specified and corresponding driver defined), then the result is processed with ident (if specified), and then finally with text (again, if specified and applicable).

In the check-out codepath, the blob content is first converted with text, and then ident and fed to filter.

Merging branches with differing checkin/checkout attributes

If you have added attributes to a file that cause the canonical repository format for that file to change, such as adding a clean/smudge filter or text/eol/ident attributes, merging anything where the attribute is not in place would normally cause merge conflicts.

To prevent these unnecessary merge conflicts, Git can be told to run a virtual check-out and check-in of all three stages of each file that needs a three-way content merge, by setting the merge.renormalize configuration variable. This prevents changes caused by check-in conversion from causing spurious merge conflicts when a converted file is merged with an unconverted file.

As long as a "smudge→clean" results in the same output as a "clean" even on files that are already smudged, this strategy will automatically resolve all filter-related conflicts. Filters that do not act in this way may cause additional merge conflicts that must be resolved manually.

### Generating diff text
diff

The attribute diff affects how Git generates diffs for particular files. It can tell Git whether to generate a textual patch for the path or to treat the path as a binary file. It can also affect what line is shown on the hunk header @@ -k,l +n,m @@ line, tell Git to use an external command to generate the diff, or ask Git to convert binary files to a text format before generating the diff.

Set

A path to which the diff attribute is set is treated as text, even when they contain byte values that normally never appear in text files, such as NUL.

Unset

A path to which the diff attribute is unset will generate Binary files differ (or a binary patch, if binary patches are enabled).

Unspecified

A path to which the diff attribute is unspecified first gets its contents inspected, and if it looks like text and is smaller than core.bigFileThreshold, it is treated as text. Otherwise it would generate Binary files differ.

String

Diff is shown using the specified diff driver. Each driver may specify one or more options, as described in the following section. The options for the diff driver "foo" are defined by the configuration variables in the "diff.foo" section of the Git config file.

Defining an external diff driver

The definition of a diff driver is done in gitconfig, not gitattributes file, so strictly speaking this manual page is a wrong place to talk about it. However...

To define an external diff driver jcdiff, add a section to your $GIT_DIR/config file (or $HOME/.gitconfig file) like this:

```
[diff "jcdiff"]

        command = j-c-diff
```

When Git needs to show you a diff for the path with diff attribute set to jcdiff, it calls the command you specified with the above configuration, i.e. j-c-diff, with 7 parameters, just like GIT_EXTERNAL_DIFF program is called. See git(1) for details.

If the program is able to ignore certain changes (similar to git diff --ignore-space-change), then also set the option trustExitCode to true. It is then expected to return exit code 1 if it finds significant changes and 0 if it doesn’t.

Setting the internal diff algorithm

The diff algorithm can be set through the diff.algorithm config key, but sometimes it may be helpful to set the diff algorithm per path. For example, one may want to use the minimal diff algorithm for .json files, and the histogram for .c files, and so on without having to pass in the algorithm through the command line each time.

First, in .gitattributes, assign the diff attribute for paths.

```
*.json diff=<name>
```

Then, define a "diff.<name>.algorithm" configuration to specify the diff algorithm, choosing from myers, patience, minimal, or histogram.

```
[diff "<name>"]

  algorithm = histogram
```

This diff algorithm applies to user facing diff output like git-diff(1), git-show(1) and is used for the --stat output as well. The merge machinery will not use the diff algorithm set through this method.

Note If diff.<name>.command is defined for path with the diff=<name> attribute, it is executed as an external diff driver (see above), and adding diff.<name>.algorithm has no effect, as the algorithm is not passed to the external diff driver.

Defining a custom hunk-header

Each group of changes (called a "hunk") in the textual diff output is prefixed with a line of the form:

```
@@ -k,l +n,m @@ TEXT
```

This is called a hunk header. The "TEXT" portion is by default a line that begins with an alphabet, an underscore or a dollar sign; this matches what GNU diff -p output uses. This default selection however is not suited for some contents, and you can use a customized pattern to make a selection.

First, in .gitattributes, you would assign the diff attribute for paths.

```
*.tex   diff=tex
```

Then, you would define a "diff.tex.xfuncname" configuration to specify a regular expression that matches a line that you would want to appear as the hunk header "TEXT". Add a section to your $GIT_DIR/config file (or $HOME/.gitconfig file) like this:

```
[diff "tex"]

        xfuncname = "^(\\\\(sub)*section\\{.*)$"
```

Note. A single level of backslashes are eaten by the configuration file parser, so you would need to double the backslashes; the pattern above picks a line that begins with a backslash, and zero or more occurrences of sub followed by section followed by open brace, to the end of line.

There are a few built-in patterns to make this easier, and tex is one of them, so you do not have to write the above in your configuration file (you still need to enable this with the attribute mechanism, via .gitattributes). The following built in patterns are available:

•ada suitable for source code in the Ada language.

•bash suitable for source code in the Bourne-Again SHell language. Covers a superset of POSIX shell function definitions.

•bibtex suitable for files with BibTeX coded references.

•cpp suitable for source code in the C and C++ languages.

•csharp suitable for source code in the C# language.

•css suitable for cascading style sheets.

•dts suitable for devicetree (DTS) files.

•elixir suitable for source code in the Elixir language.

•fortran suitable for source code in the Fortran language.

•fountain suitable for Fountain documents.

•golang suitable for source code in the Go language.

•html suitable for HTML/XHTML documents.

•java suitable for source code in the Java language.

•kotlin suitable for source code in the Kotlin language.

•markdown suitable for Markdown documents.

•matlab suitable for source code in the MATLAB and Octave languages.

•objc suitable for source code in the Objective-C language.

•pascal suitable for source code in the Pascal/Delphi language.

•perl suitable for source code in the Perl language.

•php suitable for source code in the PHP language.

•python suitable for source code in the Python language.

•ruby suitable for source code in the Ruby language.

•rust suitable for source code in the Rust language.

•scheme suitable for source code in the Scheme language.

•tex suitable for source code for LaTeX documents.

Customizing word diff

You can customize the rules that git diff --word-diff uses to split words in a line, by specifying an appropriate regular expression in the "diff.*.wordRegex" configuration variable. For example, in TeX a backslash followed by a sequence of letters forms a command, but several such commands can be run together without intervening whitespace. To separate them, use a regular expression in your $GIT_DIR/config file (or $HOME/.gitconfig file) like this:

```
[diff "tex"]

        wordRegex = "\\\\[a-zA-Z]+|[{}]|\\\\.|[^\\{}[:space:]]+"
```

A built-in pattern is provided for all languages listed in the previous section.

Performing text diffs of binary files

Sometimes it is desirable to see the diff of a text-converted version of some binary files. For example, a word processor document can be converted to an ASCII text representation, and the diff of the text shown. Even though this conversion loses some information, the resulting diff is useful for human viewing (but cannot be applied directly).

The textconv config option is used to define a program for performing such a conversion. The program should take a single argument, the name of a file to convert, and produce the resulting text on stdout.

For example, to show the diff of the exif information of a file instead of the binary information (assuming you have the exif tool installed), add the following section to your $GIT_DIR/config file (or $HOME/.gitconfig file):

```
[diff "jpg"]

        textconv = exif
```

Note The text conversion is generally a one-way conversion; in this example, we lose the actual image contents and focus just on the text data. This means that diffs generated by textconv are not suitable for applying. For this reason, only git diff and the git log family of commands (i.e., log, whatchanged, show) will perform text conversion. git format-patch will never generate this output. If you want to send somebody a text-converted diff of a binary file (e.g., because it quickly conveys the changes you have made), you should generate it separately and send it as a comment in addition to the usual binary diff that you might send.

Because text conversion can be slow, especially when doing a large number of them with git log -p, Git provides a mechanism to cache the output and use it in future diffs. To enable caching, set the "cachetextconv" variable in your diff driver’s config. For example:

```
[diff "jpg"]

        textconv = exif

        cachetextconv = true
```

This will cache the result of running "exif" on each blob indefinitely. If you change the textconv config variable for a diff driver, Git will automatically invalidate the cache entries and re-run the textconv filter. If you want to invalidate the cache manually (e.g., because your version of "exif" was updated and now produces better output), you can remove the cache manually with git update-ref -d refs/notes/textconv/jpg (where "jpg" is the name of the diff driver, as in the example above).

Choosing textconv versus external diff

If you want to show differences between binary or specially-formatted blobs in your repository, you can choose to use either an external diff command, or to use textconv to convert them to a diff-able text format. Which method you choose depends on your exact situation.

The advantage of using an external diff command is flexibility. You are not bound to find line-oriented changes, nor is it necessary for the output to resemble unified diff. You are free to locate and report changes in the most appropriate way for your data format.

A textconv, by comparison, is much more limiting. You provide a transformation of the data into a line-oriented text format, and Git uses its regular diff tools to generate the output. There are several advantages to choosing this method:

1.Ease of use. It is often much simpler to write a binary to text transformation than it is to perform your own diff. In many cases, existing programs can be used as textconv filters (e.g., exif, odt2txt).

2.Git diff features. By performing only the transformation step yourself, you can still utilize many of Git’s diff features, including colorization, word-diff, and combined diffs for merges.

3.Caching. Textconv caching can speed up repeated diffs, such as those you might trigger by running git log -p.

Marking files as binary

Git usually guesses correctly whether a blob contains text or binary data by examining the beginning of the contents. However, sometimes you may want to override its decision, either because a blob contains binary data later in the file, or because the content, while technically composed of text characters, is opaque to a human reader. For example, many postscript files contain only ASCII characters, but produce noisy and meaningless diffs.

The simplest way to mark a file as binary is to unset the diff attribute in the .gitattributes file:

```
*.ps -diff
```

This will cause Git to generate Binary files differ (or a binary patch, if binary patches are enabled) instead of a regular diff.

However, one may also want to specify other diff driver attributes. For example, you might want to use textconv to convert postscript files to an ASCII representation for human viewing, but otherwise treat them as binary files. You cannot specify both -diff and diff=ps attributes. The solution is to use the diff.*.binary config option:

```
[diff "ps"]

  textconv = ps2ascii

  binary = true
```

### Performing a three-way merge
merge

The attribute merge affects how three versions of a file are merged when a file-level merge is necessary during git merge, and other commands such as git revert and git cherry-pick.

Set

Built-in 3-way merge driver is used to merge the contents in a way similar to merge command of RCS suite. This is suitable for ordinary text files.

Unset

Take the version from the current branch as the tentative merge result, and declare that the merge has conflicts. This is suitable for binary files that do not have a well-defined merge semantics.

Unspecified

By default, this uses the same built-in 3-way merge driver as is the case when the merge attribute is set. However, the merge.default configuration variable can name different merge driver to be used with paths for which the merge attribute is unspecified.

String

3-way merge is performed using the specified custom merge driver. The built-in 3-way merge driver can be explicitly specified by asking for "text" driver; the built-in "take the current branch" driver can be requested with "binary".

Built-in merge drivers

There are a few built-in low-level merge drivers defined that can be asked for via the merge attribute.

text

Usual 3-way file level merge for text files. Conflicted regions are marked with conflict markers <<<<<<<, ======= and >>>>>>>. The version from your branch appears before the ======= marker, and the version from the merged branch appears after the ======= marker.

binary

Keep the version from your branch in the work tree, but leave the path in the conflicted state for the user to sort out.

union

Run 3-way file level merge for text files, but take lines from both versions, instead of leaving conflict markers. This tends to leave the added lines in the resulting file in random order and the user should verify the result. Do not use this if you do not understand the implications.

Defining a custom merge driver

The definition of a merge driver is done in the .git/config file, not in the gitattributes file, so strictly speaking this manual page is a wrong place to talk about it. However...

To define a custom merge driver filfre, add a section to your $GIT_DIR/config file (or $HOME/.gitconfig file) like this:

```
[merge "filfre"]

        name = feel-free merge driver

        driver = filfre %O %A %B %L %P

        recursive = binary
```

The merge.*.name variable gives the driver a human-readable name.

The ‘merge.*.driver` variable’s value is used to construct a command to run to common ancestor’s version (%O), current version (%A) and the other branches’ version (%B). These three tokens are replaced with the names of temporary files that hold the contents of these versions when the command line is built. Additionally, %L will be replaced with the conflict marker size (see below).

The merge driver is expected to leave the result of the merge in the file named with %A by overwriting it, and exit with zero status if it managed to merge them cleanly, or non-zero if there were conflicts. When the driver crashes (e.g. killed by SEGV), it is expected to exit with non-zero status that are higher than 128, and in such a case, the merge results in a failure (which is different from producing a conflict).

The merge.*.recursive variable specifies what other merge driver to use when the merge driver is called for an internal merge between common ancestors, when there are more than one. When left unspecified, the driver itself is used for both internal merge and the final merge.

The merge driver can learn the pathname in which the merged result will be stored via placeholder %P. The conflict labels to be used for the common ancestor, local head and other head can be passed by using %S, %X and %Y respectively.

conflict-marker-size

This attribute controls the length of conflict markers left in the work tree file during a conflicted merge. Only a positive integer has a meaningful effect.

For example, this line in .gitattributes can be used to tell the merge machinery to leave much longer (instead of the usual 7-character-long) conflict markers when merging the file Documentation/git-merge.adoc results in a conflict.

```
Documentation/git-merge.adoc    conflict-marker-size=32
```

### Checking whitespace errors
whitespace

The core.whitespace configuration variable allows you to define what diff and apply should consider whitespace errors for all paths in the project (See git-config(1)). This attribute gives you finer control per path.

Set

Notice all types of potential whitespace errors known to Git. The tab width is taken from the value of the core.whitespace configuration variable.

Unset

Do not notice anything as error.

Unspecified

Use the value of the core.whitespace configuration variable to decide what to notice as error.

String

Specify a comma separated list of common whitespace problems to notice in the same format as the core.whitespace configuration variable.

### Creating an archive
export-ignore

Files and directories with the attribute export-ignore won’t be added to archive files.

export-subst

If the attribute export-subst is set for a file then Git will expand several placeholders when adding this file to an archive. The expansion depends on the availability of a commit ID, i.e., if git-archive(1) has been given a tree instead of a commit or a tag then no replacement will be done. The placeholders are the same as those for the option --pretty=format: of git-log(1), except that they need to be wrapped like this: $Format:PLACEHOLDERS$ in the file. E.g. the string $Format:%H$ will be replaced by the commit hash. However, only one %(describe) placeholder is expanded per archive to avoid denial-of-service attacks.

### Packing objects
delta

Delta compression will not be attempted for blobs for paths with the attribute delta set to false.

### Viewing files in GUI tools
encoding

The value of this attribute specifies the character encoding that should be used by GUI tools (e.g. gitk(1) and git-gui(1)) to display the contents of the relevant file. Note that due to performance considerations gitk(1) does not use this attribute unless you manually enable per-file encodings in its options.

If this attribute is not set or has an invalid value, the value of the gui.encoding configuration variable is used instead (See git-config(1)).

## USING MACRO ATTRIBUTES
You do not want any end-of-line conversions applied to, nor textual diffs produced for, any binary file you track. You would need to specify e.g.

```
*.jpg -text -diff
```

but that may become cumbersome, when you have many attributes. Using macro attributes, you can define an attribute that, when set, also sets or unsets a number of other attributes at the same time. The system knows a built-in macro attribute, binary:

```
*.jpg binary
```

Setting the "binary" attribute also unsets the "text" and "diff" attributes as above. Note that macro attributes can only be "Set", though setting one might have the effect of setting or unsetting other attributes or even returning other attributes to the "Unspecified" state.

## DEFINING MACRO ATTRIBUTES
Custom macro attributes can be defined only in top-level gitattributes files ($GIT_DIR/info/attributes, the .gitattributes file at the top level of the working tree, or the global or system-wide gitattributes files), not in .gitattributes files in working tree subdirectories. The built-in macro attribute "binary" is equivalent to:

```
[attr]binary -diff -merge -text
```

## NOTES
Git does not follow symbolic links when accessing a .gitattributes file in the working tree. This keeps behavior consistent when the file is accessed from the index or a tree versus from the filesystem.

## EXAMPLES
If you have these three gitattributes file:

```
(in $GIT_DIR/info/attributes)
a*      foo !bar -baz
(in .gitattributes)
abc     foo bar baz
(in t/.gitattributes)
ab*     merge=filfre
abc     -foo -bar
*.c     frotz
```

the attributes given to path t/abc are computed as follows:

1.By examining t/.gitattributes (which is in the same directory as the path in question), Git finds that the first line matches. merge attribute is set. It also finds that the second line matches, and attributes foo and bar are unset.

2.Then it examines .gitattributes (which is in the parent directory), and finds that the first line matches, but t/.gitattributes file already decided how merge, foo and bar attributes should be given to this path, so it leaves foo and bar unset. Attribute baz is set.

3.Finally it examines $GIT_DIR/info/attributes. This file is used to override the in-tree settings. The first line is a match, and foo is set, bar is reverted to unspecified state, and baz is unset.

As the result, the attributes assignment to t/abc becomes:

```
foo     set to true
bar     unspecified
baz     set to false
merge   set to string value "filfre"
frotz   unspecified
```

## SEE ALSO
git-check-attr(1).

## GIT
Part of the git(1) suite


gitformat-bundle

title: gitformat-bundle(5)

summary: The bundle file format

text:
# gitformat-bundle(5)

## NAME
gitformat-bundle - The bundle file format

## SYNOPSIS

```
*.bundle
*.bdl
```

## DESCRIPTION
The Git bundle format is a format that represents both refs and Git objects. A bundle is a header in a format similar to git-show-ref(1) followed by a pack in *.pack format.

The format is created and read by the git-bundle(1) command, and supported by e.g. git-fetch(1) and git-clone(1).

## FORMAT
We will use ABNF notation to define the Git bundle format. See gitprotocol-common(5) for the details.

A v2 bundle looks like this:

```
bundle    = signature *prerequisite *reference LF pack
signature = "# v2 git bundle" LF
prerequisite = "-" obj-id SP comment LF
comment      = *CHAR
reference    = obj-id SP refname LF
pack         = ... ; packfile
```

A v3 bundle looks like this:

```
bundle    = signature *capability *prerequisite *reference LF pack
signature = "# v3 git bundle" LF
capability   = "@" key ["=" value] LF
prerequisite = "-" obj-id SP comment LF
comment      = *CHAR
reference    = obj-id SP refname LF
key          = 1*(ALPHA / DIGIT / "-")
value        = *(%01-09 / %0b-FF)
pack         = ... ; packfile
```

## SEMANTICS
A Git bundle consists of several parts.

•"Capabilities", which are only in the v3 format, indicate functionality that the bundle requires to be read properly.

•"Prerequisites" list the objects that are NOT included in the bundle and the reader of the bundle MUST already have, in order to use the data in the bundle. The objects stored in the bundle may refer to prerequisite objects and anything reachable from them (e.g. a tree object in the bundle can reference a blob that is reachable from a prerequisite) and/or expressed as a delta against prerequisite objects.

•"References" record the tips of the history graph, iow, what the reader of the bundle CAN "git fetch" from it.

•"Pack" is the pack data stream "git fetch" would send, if you fetch from a repository that has the references recorded in the "References" above into a repository that has references pointing at the objects listed in "Prerequisites" above.

In the bundle format, there can be a comment following a prerequisite obj-id. This is a comment and it has no specific meaning. The writer of the bundle MAY put any string here. The reader of the bundle MUST ignore the comment.

### Note on shallow clones and Git bundles
Note that the prerequisites do not represent a shallow-clone boundary. The semantics of the prerequisites and the shallow-clone boundaries are different, and the Git bundle v2 format cannot represent a shallow clone repository.

## CAPABILITIES
Because there is no opportunity for negotiation, unknown capabilities cause git bundle to abort.

•object-format specifies the hash algorithm in use, and can take the same values as the extensions.objectFormat configuration value.

•filter specifies an object filter as in the --filter option in git-rev-list(1). The resulting pack-file must be marked as a .promisor pack-file after it is unbundled.

## GIT
Part of the git(1) suite

branch: sisyphus


gitformat-chunk

title: gitformat-chunk(5)

summary: Chunk\-based file formats

text:
# gitformat-chunk(5)

## NAME
gitformat-chunk - Chunk-based file formats

## SYNOPSIS
Used by gitformat-commit-graph(5) and the "MIDX" format (see the pack format documentation in gitformat-pack(5)).

## DESCRIPTION
Some file formats in Git use a common concept of "chunks" to describe sections of the file. This allows structured access to a large file by scanning a small "table of contents" for the remaining data. This common format is used by the commit-graph and multi-pack-index files. See the multi-pack-index format in gitformat-pack(5) and the commit-graph format in gitformat-commit-graph(5) for how they use the chunks to describe structured data.

A chunk-based file format begins with some header information custom to that format. That header should include enough information to identify the file type, format version, and number of chunks in the file. From this information, that file can determine the start of the chunk-based region.

The chunk-based region starts with a table of contents describing where each chunk starts and ends. This consists of (C+1) rows of 12 bytes each, where C is the number of chunks. Consider the following table:

```
| Chunk ID (4 bytes) | Chunk Offset (8 bytes) |
|--------------------|------------------------|
| ID[0]              | OFFSET[0]              |
| ...                | ...                    |
| ID[C]              | OFFSET[C]              |
| 0x0000             | OFFSET[C+1]            |
```

Each row consists of a 4-byte chunk identifier (ID) and an 8-byte offset. Each integer is stored in network-byte order.

The chunk identifier ID[i] is a label for the data stored within this file from OFFSET[i] (inclusive) to OFFSET[i+1] (exclusive). Thus, the size of the i`th chunk is equal to the difference between `OFFSET[i+1] and OFFSET[i]. This requires that the chunk data appears contiguously in the same order as the table of contents.

The final entry in the table of contents must be four zero bytes. This confirms that the table of contents is ending and provides the offset for the end of the chunk-based data.

Note: The chunk-based format expects that the file contains at least a trailing hash after OFFSET[C+1].

Functions for working with chunk-based file formats are declared in chunk-format.h. Using these methods provide extra checks that assist developers when creating new file formats.

## WRITING CHUNK-BASED FILE FORMATS
To write a chunk-based file format, create a struct chunkfile by calling init_chunkfile() and pass a struct hashfile pointer. The caller is responsible for opening the hashfile and writing header information so the file format is identifiable before the chunk-based format begins.

Then, call add_chunk() for each chunk that is intended for writing. This populates the chunkfile with information about the order and size of each chunk to write. Provide a chunk_write_fn function pointer to perform the write of the chunk data upon request.

Call write_chunkfile() to write the table of contents to the hashfile followed by each of the chunks. This will verify that each chunk wrote the expected amount of data so the table of contents is correct.

Finally, call free_chunkfile() to clear the struct chunkfile data. The caller is responsible for finalizing the hashfile by writing the trailing hash and closing the file.

## READING CHUNK-BASED FILE FORMATS
To read a chunk-based file format, the file must be opened as a memory-mapped region. The chunk-format API expects that the entire file is mapped as a contiguous memory region.

Initialize a struct chunkfile pointer with init_chunkfile(NULL).

After reading the header information from the beginning of the file, including the chunk count, call read_table_of_contents() to populate the struct chunkfile with the list of chunks, their offsets, and their sizes.

Extract the data information for each chunk using pair_chunk() or read_chunk():

•pair_chunk() assigns a given pointer with the location inside the memory-mapped file corresponding to that chunk’s offset. If the chunk does not exist, then the pointer is not modified.

•read_chunk() takes a chunk_read_fn function pointer and calls it with the appropriate initial pointer and size information. The function is not called if the chunk does not exist. Use this method to read chunks if you need to perform immediate parsing or if you need to execute logic based on the size of the chunk.

After calling these methods, call free_chunkfile() to clear the struct chunkfile data. This will not close the memory-mapped region. Callers are expected to own that data for the timeframe the pointers into the region are needed.

## EXAMPLES
These file formats use the chunk-format API, and can be used as examples for future formats:

•commit-graph: see write_commit_graph_file() and parse_commit_graph() in commit-graph.c for how the chunk-format API is used to write and parse the commit-graph file format documented in the commit-graph file format in gitformat-commit-graph(5).

•multi-pack-index: see write_midx_internal() and load_multi_pack_index() in midx.c for how the chunk-format API is used to write and parse the multi-pack-index file format documented in the multi-pack-index file format section of gitformat-pack(5).

## GIT
Part of the git(1) suite


gitformat-commit-graph

title: gitformat-commit-graph(5)

summary: Git commit\-graph format

text:
# gitformat-commit-graph(5)

## NAME
gitformat-commit-graph - Git commit-graph format

## SYNOPSIS

```
$GIT_DIR/objects/info/commit-graph
$GIT_DIR/objects/info/commit-graphs/*
```

## DESCRIPTION
The Git commit-graph stores a list of commit OIDs and some associated metadata, including:

•The generation number of the commit.

•The root tree OID.

•The commit date.

•The parents of the commit, stored using positional references within the graph file.

•The Bloom filter of the commit carrying the paths that were changed between the commit and its first parent, if requested.

These positional references are stored as unsigned 32-bit integers corresponding to the array position within the list of commit OIDs. Due to some special constants we use to track parents, we can store at most (1 << 30) + (1 << 29) + (1 << 28) - 1 (around 1.8 billion) commits.

## COMMIT-GRAPH FILES HAVE THE FOLLOWING FORMAT:
In order to allow extensions that add extra data to the graph, we organize the body into "chunks" and provide a binary lookup table at the beginning of the body. The header includes certain values, such as number of chunks and hash type.

All multi-byte numbers are in network byte order.

### HEADER:

```
4-byte signature:

    The signature is: {'C', 'G', 'P', 'H'}
```

```
1-byte version number:

    Currently, the only valid version is 1.
```

```
1-byte Hash Version

    We infer the hash length (H) from this value:

      1 => SHA-1

      2 => SHA-256

    If the hash type does not match the repository's hash algorithm, the

    commit-graph file should be ignored with a warning presented to the

    user.
```

```
1-byte number (C) of "chunks"
```

```
1-byte number (B) of base commit-graphs

    We infer the length (H*B) of the Base Graphs chunk

    from this value.
```

### CHUNK LOOKUP:

```
(C + 1) * 12 bytes listing the table of contents for the chunks:

    First 4 bytes describe the chunk id. Value 0 is a terminating label.

    Other 8 bytes provide the byte-offset in current file for chunk to

    start. (Chunks are ordered contiguously in the file, so you can infer

    the length using the next chunk position if necessary.) Each chunk

    ID appears at most once.
```

```
The CHUNK LOOKUP matches the table of contents from
the chunk-based file format, see linkgit:gitformat-chunk[5]
```

```
The remaining data in the body is described one chunk at a time, and
these chunks may be given in any order. Chunks are required unless
otherwise specified.
```

### CHUNK DATA:
OID Fanout (ID: {O, I, D, F}) (256 * 4 bytes)

```
The ith entry, F[i], stores the number of OIDs with first
byte at most i. Thus F[255] stores the total
number of commits (N).
```

OID Lookup (ID: {O, I, D, L}) (N * H bytes)

```
The OIDs for all commits in the graph, sorted in ascending order.
```

Commit Data (ID: {C, D, A, T }) (N * (H + 16) bytes)

•The first H bytes are for the OID of the root tree.

•The next 8 bytes are for the positions of the first two parents of the ith commit. Stores value 0x70000000 if no parent in that position. If there are more than two parents, the second value has its most-significant bit on and the other bits store an array position into the Extra Edge List chunk.

•The next 8 bytes store the topological level (generation number v1) of the commit and the commit time in seconds since EPOCH. The generation number uses the higher 30 bits of the first 4 bytes, while the commit time uses the 32 bits of the second 4 bytes, along with the lowest 2 bits of the lowest byte, storing the 33rd and 34th bit of the commit time.

Generation Data (ID: {G, D, A, 2 }) (N * 4 bytes) [Optional]

•This list of 4-byte values store corrected commit date offsets for the commits, arranged in the same order as commit data chunk.

•If the corrected commit date offset cannot be stored within 31 bits, the value has its most-significant bit on and the other bits store the position of corrected commit date into the Generation Data Overflow chunk.

•Generation Data chunk is present only when commit-graph file is written by compatible versions of Git and in case of split commit-graph chains, the topmost layer also has Generation Data chunk.

Generation Data Overflow (ID: {G, D, O, 2 }) [Optional]

•This list of 8-byte values stores the corrected commit date offsets for commits with corrected commit date offsets that cannot be stored within 31 bits.

•Generation Data Overflow chunk is present only when Generation Data chunk is present and at least one corrected commit date offset cannot be stored within 31 bits.

Extra Edge List (ID: {E, D, G, E}) [Optional]

```
This list of 4-byte values store the second through nth parents for
all octopus merges. The second parent value in the commit data stores
an array position within this list along with the most-significant bit
on. Starting at that array position, iterate through this list of commit
positions for the parents until reaching a value with the most-significant
bit on. The other bits correspond to the position of the last parent.
```

Bloom Filter Index (ID: {B, I, D, X}) (N * 4 bytes) [Optional]

•The ith entry, BIDX[i], stores the number of bytes in all Bloom filters from commit 0 to commit i (inclusive) in lexicographic order. The Bloom filter for the i-th commit spans from BIDX[i-1] to BIDX[i] (plus header length), where BIDX[-1] is 0.

•The BIDX chunk is ignored if the BDAT chunk is not present.

Bloom Filter Data (ID: {B, D, A, T}) [Optional]

•It starts with header consisting of three unsigned 32-bit integers:

•Version of the hash algorithm being used. We currently support value 2 which corresponds to the 32-bit version of the murmur3 hash implemented exactly as described in https://en.wikipedia.org/wiki/MurmurHash#Algorithm and the double hashing technique using seed values 0x293ae76f and 0x7e646e2 as described in https://doi.org/10.1007/978-3-540-30494-4_26 "Bloom Filters in Probabilistic Verification". Version 1 Bloom filters have a bug that appears when char is signed and the repository has path names that have characters >= 0x80; Git supports reading and writing them, but this ability will be removed in a future version of Git.

•The number of times a path is hashed and hence the number of bit positions that cumulatively determine whether a file is present in the commit.

•The minimum number of bits b per entry in the Bloom filter. If the filter contains n entries, then the filter size is the minimum number of 64-bit words that contain n*b bits.

•The rest of the chunk is the concatenation of all the computed Bloom filters for the commits in lexicographic order.

•Note: Commits with no changes or more than 512 changes have Bloom filters of length one, with either all bits set to zero or one respectively.

•The BDAT chunk is present if and only if BIDX is present.

Base Graphs List (ID: {B, A, S, E}) [Optional]

```
This list of H-byte hashes describe a set of B commit-graph files that
form a commit-graph chain. The graph position for the ith commit in this
file's OID Lookup chunk is equal to i plus the number of commits in all
base graphs.  If B is non-zero, this chunk must exist.
```

### TRAILER:

```
H-byte HASH-checksum of all of the above.
```

## HISTORICAL NOTES:
The Generation Data (GDA2) and Generation Data Overflow (GDO2) chunks have the number 2 in their chunk IDs because a previous version of Git wrote possibly erroneous data in these chunks with the IDs "GDAT" and "GDOV". By changing the IDs, newer versions of Git will silently ignore those older chunks and write the new information without trusting the incorrect data.

## GIT
Part of the git(1) suite


gitformat-index

title: gitformat-index(5)

summary: Git index format

text:
# gitformat-index(5)

## NAME
gitformat-index - Git index format

## SYNOPSIS

```
$GIT_DIR/index
```

## DESCRIPTION
Git index format

## THE GIT INDEX FILE HAS THE FOLLOWING FORMAT

```
All binary numbers are in network byte order.
In a repository using the traditional SHA-1, checksums and object IDs
(object names) mentioned below are all computed using SHA-1.  Similarly,
in SHA-256 repositories, these values are computed using SHA-256.
Version 2 is described here unless stated otherwise.
```

•A 12-byte header consisting of

```
4-byte signature:

  The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache")
```

```
4-byte version number:

  The current supported versions are 2, 3 and 4.
```

```
32-bit number of index entries.
```

•A number of sorted index entries (see below).

•Extensions

```
Extensions are identified by signature. Optional extensions can
be ignored if Git does not understand them.
```

```
4-byte extension signature. If the first byte is 'A'..'Z' the
extension is optional and can be ignored.
```

```
32-bit size of the extension
```

```
Extension data
```

•Hash checksum over the content of the index file before this checksum.

## INDEX ENTRY

```
Index entries are sorted in ascending order on the name field,
interpreted as a string of unsigned bytes (i.e. memcmp() order, no
localization, no special casing of directory separator '/'). Entries
with the same name are sorted by their stage field.
```

```
An index entry typically represents a file. However, if sparse-checkout
is enabled in cone mode (`core.sparseCheckoutCone` is enabled) and the
`extensions.sparseIndex` extension is enabled, then the index may
contain entries for directories outside of the sparse-checkout definition.
These entries have mode `040000`, include the `SKIP_WORKTREE` bit, and
the path ends in a directory separator.
```

```
32-bit ctime seconds, the last time a file's metadata changed

  this is stat(2) data
```

```
32-bit ctime nanosecond fractions

  this is stat(2) data
```

```
32-bit mtime seconds, the last time a file's data changed

  this is stat(2) data
```

```
32-bit mtime nanosecond fractions

  this is stat(2) data
```

```
32-bit dev

  this is stat(2) data
```

```
32-bit ino

  this is stat(2) data
```

```
32-bit mode, split into (high to low bits)
```

```
16-bit unused, must be zero
```

```
4-bit object type

  valid values in binary are 1000 (regular file), 1010 (symbolic link)

  and 1110 (gitlink)
```

```
3-bit unused, must be zero
```

```
9-bit unix permission. Only 0755 and 0644 are valid for regular files.
Symbolic links and gitlinks have value 0 in this field.
```

```
32-bit uid

  this is stat(2) data
```

```
32-bit gid

  this is stat(2) data
```

```
32-bit file size

  This is the on-disk size from stat(2), truncated to 32-bit.
```

```
Object name for the represented object
```

```
A 16-bit 'flags' field split into (high to low bits)
```

```
1-bit assume-valid flag
```

```
1-bit extended flag (must be zero in version 2)
```

```
2-bit stage (during merge)
```

```
12-bit name length if the length is less than 0xFFF; otherwise 0xFFF
is stored in this field.
```

```
(Version 3 or later) A 16-bit field, only applicable if the
"extended flag" above is 1, split into (high to low bits).
```

```
1-bit reserved for future
```

```
1-bit skip-worktree flag (used by sparse checkout)
```

```
1-bit intent-to-add flag (used by "git add -N")
```

```
13-bit unused, must be zero
```

```
Entry path name (variable length) relative to top level directory

  (without leading slash). '/' is used as path separator. The special

  path components ".", ".." and ".git" (without quotes) are disallowed.

  Trailing slash is also disallowed.
```

```
The exact encoding is undefined, but the '.' and '/' characters
are encoded in 7-bit ASCII and the encoding cannot contain a NUL
byte (iow, this is a UNIX pathname).
```

```
(Version 4) In version 4, the entry path name is prefix-compressed

  relative to the path name for the previous entry (the very first

  entry is encoded as if the path name for the previous entry is an

  empty string).  At the beginning of an entry, an integer N in the

  variable width encoding (the same encoding as the offset is encoded

  for OFS_DELTA pack entries; see linkgit:gitformat-pack[5]) is stored, followed

  by a NUL-terminated string S.  Removing N bytes from the end of the

  path name for the previous entry, and replacing it with the string S

  yields the path name for this entry.
```

```
1-8 nul bytes as necessary to pad the entry to a multiple of eight bytes
while keeping the name NUL-terminated.
```

```
(Version 4) In version 4, the padding after the pathname does not
exist.
```

```
Interpretation of index entries in split index mode is completely
different. See below for details.
```

## EXTENSIONS

### Cache tree

```
Since the index does not record entries for directories, the cache
entries cannot describe tree objects that already exist in the object
database for regions of the index that are unchanged from an existing
commit. The cache tree extension stores a recursive tree structure that
describes the trees that already exist and completely match sections of
the cache entries. This speeds up tree object generation from the index
for a new commit by only computing the trees that are "new" to that
commit. It also assists when comparing the index to another tree, such
as `HEAD^{tree}`, since sections of the index can be skipped when a tree
comparison demonstrates equality.
```

```
The recursive tree structure uses nodes that store a number of cache
entries, a list of subnodes, and an object ID (OID). The OID references
the existing tree for that node, if it is known to exist. The subnodes
correspond to subdirectories that themselves have cache tree nodes. The
number of cache entries corresponds to the number of cache entries in
the index that describe paths within that tree's directory.
```

```
The extension tracks the full directory structure in the cache tree
extension, but this is generally smaller than the full cache entry list.
```

```
When a path is updated in index, Git invalidates all nodes of the
recursive cache tree corresponding to the parent directories of that
path. We store these tree nodes as being "invalid" by using "-1" as the
number of cache entries. Invalid nodes still store a span of index
entries, allowing Git to focus its efforts when reconstructing a full
cache tree.
```

```
The signature for this extension is { 'T', 'R', 'E', 'E' }.
```

```
A series of entries fill the entire extension; each of which
consists of:
```

•NUL-terminated path component (relative to its parent directory);

•ASCII decimal number of entries in the index that is covered by the tree this entry represents (entry_count);

•A space (ASCII 32);

•ASCII decimal number that represents the number of subtrees this tree has;

•A newline (ASCII 10); and

•Object name for the object that would result from writing this span of index as a tree.

```
An entry can be in an invalidated state and is represented by having
a negative number in the entry_count field. In this case, there is no
object name and the next entry starts immediately after the newline.
When writing an invalid entry, -1 should always be used as entry_count.
```

```
The entries are written out in the top-down, depth-first order.  The
first entry represents the root level of the repository, followed by the
first subtree--let's call this A--of the root level (with its name
relative to the root level), followed by the first subtree of A (with
its name relative to A), and so on. The specified number of subtrees
indicates when the current level of the recursive stack is complete.
```

### Resolve undo

```
A conflict is represented in the index as a set of higher stage entries.
When a conflict is resolved (e.g. with "git add path"), these higher
stage entries will be removed and a stage-0 entry with proper resolution
is added.
```

```
When these higher stage entries are removed, they are saved in the
resolve undo extension, so that conflicts can be recreated (e.g. with
"git checkout -m"), in case users want to redo a conflict resolution
from scratch.
```

```
The signature for this extension is { 'R', 'E', 'U', 'C' }.
```

```
A series of entries fill the entire extension; each of which
consists of:
```

•NUL-terminated pathname the entry describes (relative to the root of the repository, i.e. full pathname);

•Three NUL-terminated ASCII octal numbers, entry mode of entries in stage 1 to 3 (a missing stage is represented by "0" in this field); and

•At most three object names of the entry in stages from 1 to 3 (nothing is written for a missing stage).

### Split index

```
In split index mode, the majority of index entries could be stored
in a separate file. This extension records the changes to be made on
top of that to produce the final index.
```

```
The signature for this extension is { 'l', 'i', 'n', 'k' }.
```

```
The extension consists of:
```

•Hash of the shared index file. The shared index file path is $GIT_DIR/sharedindex.<hash>. If all bits are zero, the index does not require a shared index file.

•An ewah-encoded delete bitmap, each bit represents an entry in the shared index. If a bit is set, its corresponding entry in the shared index will be removed from the final index. Note, because a delete operation changes index entry positions, but we do need original positions in replace phase, it’s best to just mark entries for removal, then do a mass deletion after replacement.

•An ewah-encoded replace bitmap, each bit represents an entry in the shared index. If a bit is set, its corresponding entry in the shared index will be replaced with an entry in this index file. All replaced entries are stored in sorted order in this index. The first "1" bit in the replace bitmap corresponds to the first index entry, the second "1" bit to the second entry and so on. Replaced entries may have empty path names to save space.

```
The remaining index entries after replaced ones will be added to the
final index. These added entries are also sorted by entry name then
stage.
```

## UNTRACKED CACHE

```
Untracked cache saves the untracked file list and necessary data to
verify the cache. The signature for this extension is { 'U', 'N',
'T', 'R' }.
```

```
The extension starts with
```

•A sequence of NUL-terminated strings, preceded by the size of the sequence in variable width encoding. Each string describes the environment where the cache can be used.

•Stat data of $GIT_DIR/info/exclude. See "Index entry" section from ctime field until "file size".

•Stat data of core.excludesFile

•32-bit dir_flags (see struct dir_struct)

•Hash of $GIT_DIR/info/exclude. A null hash means the file does not exist.

•Hash of core.excludesFile. A null hash means the file does not exist.

•NUL-terminated string of per-dir exclude file name. This usually is ".gitignore".

•The number of following directory blocks, variable width encoding. If this number is zero, the extension ends here with a following NUL.

•A number of directory blocks in depth-first-search order, each consists of

•The number of untracked entries, variable width encoding.

•The number of sub-directory blocks, variable width encoding.

•The directory name terminated by NUL.

•A number of untracked file/dir names terminated by NUL.

The remaining data of each directory block is grouped by type:

•An ewah bitmap, the n-th bit marks whether the n-th directory has valid untracked cache entries.

•An ewah bitmap, the n-th bit records "check-only" bit of read_directory_recursive() for the n-th directory.

•An ewah bitmap, the n-th bit indicates whether hash and stat data is valid for the n-th directory and exists in the next data.

•An array of stat data. The n-th data corresponds with the n-th "one" bit in the previous ewah bitmap.

•An array of hashes. The n-th hash corresponds with the n-th "one" bit in the previous ewah bitmap.

•One NUL.

## FILE SYSTEM MONITOR CACHE

```
The file system monitor cache tracks files for which the core.fsmonitor
hook has told us about changes.  The signature for this extension is
{ 'F', 'S', 'M', 'N' }.
```

```
The extension starts with
```

•32-bit version number: the current supported versions are 1 and 2.

•(Version 1) 64-bit time: the extension data reflects all changes through the given time which is stored as the nanoseconds elapsed since midnight, January 1, 1970.

•(Version 2) A null terminated string: an opaque token defined by the file system monitor application. The extension data reflects all changes relative to that token.

•32-bit bitmap size: the size of the CE_FSMONITOR_VALID bitmap.

•An ewah bitmap, the n-th bit indicates whether the n-th index entry is not CE_FSMONITOR_VALID.

## END OF INDEX ENTRY

```
The End of Index Entry (EOIE) is used to locate the end of the variable
length index entries and the beginning of the extensions. Code can take
advantage of this to quickly locate the index extensions without having
to parse through all of the index entries.
```

```
Because it must be able to be loaded before the variable length cache
entries and other index extensions, this extension must be written last.
The signature for this extension is { 'E', 'O', 'I', 'E' }.
```

```
The extension consists of:
```

•32-bit offset to the end of the index entries

•Hash over the extension types and their sizes (but not their contents). E.g. if we have "TREE" extension that is N-bytes long, "REUC" extension that is M-bytes long, followed by "EOIE", then the hash would be:

```
Hash("TREE" + <binary-representation-of-N> +

        "REUC" + <binary-representation-of-M>)
```

## INDEX ENTRY OFFSET TABLE

```
The Index Entry Offset Table (IEOT) is used to help address the CPU
cost of loading the index by enabling multi-threading the process of
converting cache entries from the on-disk format to the in-memory format.
The signature for this extension is { 'I', 'E', 'O', 'T' }.
```

```
The extension consists of:
```

•32-bit version (currently 1)

•A number of index offset entries each consisting of:

•32-bit offset from the beginning of the file to the first cache entry in this block of entries.

•32-bit count of cache entries in this block

## SPARSE DIRECTORY ENTRIES

```
When using sparse-checkout in cone mode, some entire directories within
the index can be summarized by pointing to a tree object instead of the
entire expanded list of paths within that tree. An index containing such
entries is a "sparse index". Index format versions 4 and less were not
implemented with such entries in mind. Thus, for these versions, an
index containing sparse directory entries will include this extension
with signature { 's', 'd', 'i', 'r' }. Like the split-index extension,
tools should avoid interacting with a sparse index unless they understand
this extension.
```

## GIT
Part of the git(1) suite