text

This attribute enables and controls end-of-line normalization. When a text file is normalized, its line endings are converted to LF in the repository. To control what line ending style is used in the working directory, use the eol attribute for a single file and the core.eol configuration variable for all text files. Note that core.autocrlf overrides core.eol

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

eol

This attribute sets a specific line-ending style to be used in the working directory. It enables end-of-line conversion without any content checks, effectively setting the text attribute.

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

From a clean working directory:

$ echo "* text=auto" >.gitattributes
$ rm .git/index     # Remove the index to force Git to
$ git reset         # re-scan the working directory
$ git status        # Show files that will be normalized
$ git add -u
$ git add .gitattributes
$ 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…​

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.

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 a packet format (pkt-line, see technical/protocol-common.txt) based protocol over standard input and standard output as follows. All packets, except for the "*CONTENT" packets and the "0000" flush packet, are considered text and therefore are terminated by a LF.

Git starts the filter when it encounters the first file that needs to be cleaned or smudged. After the filter started Git sends a welcome message ("git-filter-client"), a list of supported protocol version numbers, and a flush packet. Git expects to read a welcome response message ("git-filter-server"), exactly one protocol version number from the previously sent list, and a flush packet. All further communication will be based on the selected version. The remaining protocol description below documents "version=2". Please note that "version=42" in the example below does not exist and is only there to illustrate how the protocol would look like with more than one version.

After the version negotiation Git sends a list of all capabilities that it supports and a flush packet. Git expects to read a list of desired capabilities, which must be a subset of the supported capabilities list, and a flush packet as response:

packet:          git> git-filter-client
packet:          git> version=2
packet:          git> version=42
packet:          git> 0000
packet:          git< git-filter-server
packet:          git< version=2
packet:          git< 0000
packet:          git> capability=clean
packet:          git> capability=smudge
packet:          git> capability=not-yet-invented
packet:          git> 0000
packet:          git< capability=clean
packet:          git< capability=smudge
packet:          git< 0000

Supported filter capabilities in version 2 are "clean" and "smudge".

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.

After the filter has processed a blob it is expected to wait for the next "key=value" list containing a command. Git will close the command pipe on exit. The filter is expected to detect EOF and exit gracefully on its own. Git will wait until the filter process has stopped.

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 a file when resolving a three-way 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.

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.

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.

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:

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

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:

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

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.

Built-in merge drivers

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

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 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. 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.

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.

conflict-marker-size

This attribute controls the length of conflict markers left in the work tree file during a conflicted merge. Only setting to the value to a positive integer has any 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.txt results in a conflict.

Documentation/git-merge.txt        conflict-marker-size=32

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.

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.

delta

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

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]).