Documentation/gitattributes.txt - jrn/git - Git at Google

 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:

 	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 linkgit: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 linkgit: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.


 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
 ----------------------------------------------------------------


 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
 linkgit: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 linkgit: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.


 GIT
 ---
 Part of the linkgit:git[1] suite
	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:

	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 linkgit: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 linkgit: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.


	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
	----------------------------------------------------------------


	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
	linkgit: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 linkgit: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.


	GIT
	---
	Part of the linkgit:git[1] suite