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gitattributes - defining attributes per path
$GIT_DIR/info/attributes, gitattributes
A `gitattributes` file is a simple text file that gives
`attributes` to pathnames.
Each line in `gitattributes` file is of form:
glob attr1 attr2 ...
That is, a glob pattern followed by an attributes list,
separated by whitespaces. When the glob pattern matches the
path in question, the attributes listed on the line are given to
the path.
Each attribute can be in one of these states for a given path:
The path has the attribute with special value "true";
this is specified by listing only the name of the
attribute in the attribute list.
The path has the attribute with special value "false";
this is specified by listing the name of the attribute
prefixed with a dash `-` in the attribute list.
Set to a value::
The path has the attribute with specified string value;
this is specified by listing the name of the attribute
followed by an equal sign `=` and its value in the
attribute list.
No glob pattern matches the path, and nothing says if
the path has or does not have the attribute.
When more than one glob pattern matches the path, a later line
overrides an earlier line.
When deciding what attributes are assigned to a path, git
consults `$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 `!`.
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
The attribute `crlf` affects how the contents stored in the
repository are copied to the working tree files when commands
such as `git checkout` and `git merge` run. It also affects how
git stores the contents you prepare in the working tree in the
repository upon `git add` and `git commit`.
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
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 `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.
Generating diff text
The attribute `diff` affects if `git diff` generates textual
patch for the path or just says `Binary files differ`.
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.
A path to which the `diff` attribute is unset will
generate `Binary files differ`.
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`.
Any other value set to `diff` attribute is ignored and git acts
as if the attribute is left unspecified.
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`.
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.
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.
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.
Any other string value::
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 by "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
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
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.
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
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