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).

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, three 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.

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.

Interaction between checkin/checkout attributes

In the check-in codepath, the worktree file is first converted with ident (if specified), and then with crlf (again, if specified and applicable).

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

filter

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

A filter driver consists of clean command and smudge command, either of which can be left unspecified. Upon checkout, when 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, clean command is used to convert the contents of worktree file upon checkin.

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 keyword here is "more convenient" and not "turning something unusable into usable". In other words, it is "hanging yourself because we gave you a long rope" if your project uses filtering mechanism in such a way that it makes your project unusable unless the checkout is done with a specific filter in effect.

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.

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.

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 gitlink:git[7] for details.

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".

Defining a custom merge driver

The definition of a merge 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 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.

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 diretory 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/gitattributes. 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 assignement 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 gitlink:git[7] suite