# gitattributes(5) Manual Page

## 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:

    glob    attr1 attr2 ...

That is, a glob pattern followed by an attributes list, separated by whitespaces. When the glob 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 glob 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 glob pattern matches the path, a later line overrides an earlier line. This overriding is done per attribute.

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 (the further the directory that contains `.gitattributes` is from the path in question, the lower its precedence).

If you wish to affect only a single repository (i.e., to assign attributes to files that are particular to one user's workflow), 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.

Sometimes you would need to override an 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 `!`.

## 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 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`.

#### `crlf`

This attribute controls the line-ending convention.

Set

  Setting the `crlf` attribute on a path is meant to mark the path as a "text" file. core.autocrlf conversion takes place without guessing the content type by inspection.

Unset

  Unsetting the `crlf` attribute on a path is meant to mark the path as a "binary" file. The path never goes through line endings conversion upon checkin/checkout.

Unspecified

  Unspecified `crlf` attribute tells git to apply the `core.autocrlf` conversion when the file content looks like text.

Set to string value "input"

  This is similar to setting the attribute to `true`, but also forces git to act as if `core.autocrlf` is set to `input` for the path.

Any other value set to `crlf` attribute is ignored and git acts as if the attribute is left unspecified.

#### The `core.autocrlf` conversion

If the configuration variable `core.autocrlf` is false, no conversion is done.

When `core.autocrlf` is true, it means that the platform wants CRLF line endings for files in the working tree, and you want to convert them back to the normal LF line endings when checking in to the repository.

When `core.autocrlf` is set to "input", line endings are converted to LF upon checkin, but there is no conversion done upon checkout.

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.

#### `ident`

When the attribute `ident` is set to a path, git replaces `$Id$` in the blob object with `$Id:`, followed by 40-character hexadecimal blob object name, followed by a dollar sign `$` 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.

A missing filter driver definition in the config is not an error but makes the filter a no-op passthru.

The content filtering is done to massage the content into a shape that is more convenient for the platform, filesystem, and the user to use. 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.

#### 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 `crlf` (again, if specified and applicable).

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

### Generating diff text

The attribute `diff` affects if `git diff` generates textual patch for the path or just says `Binary files differ`. It also can affect what line is shown on the hunk header `@@ -k,l +n,m @@` line.

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`.

Unspecified

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

String

  Diff is shown using the specified custom diff driver. The driver program is given its input using the same calling convention as used for GIT_EXTERNAL_DIFF program. This name is also used for custom hunk header selection.

#### Defining a custom 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 a custom 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.

#### Defining a custom hunk-header

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

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

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

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

    *.tex   diff=tex

Then, you would define "diff.tex.funcname" configuration to specify a regular expression that matches a line that you would want to appear as the hunk header, like this:

    [diff "tex"]
            funcname = "^\\(\\\\\\(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`). Another built-in pattern is defined for `java` that defines a pattern suitable for program text in Java language.

### Performing a three-way merge

The attribute `merge` affects how three versions of a file is merged when a file-level merge is necessary during `git merge`, and other programs 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 does not have a well-defined merge semantics.

Unspecified

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

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.

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.

### 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.

Unset

  Do not notice anything as error.

Unspecified

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

String

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

### Creating an archive

#### `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.

## EXAMPLE

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

## GIT

Part of the git(1) suite