GITATTRIBUTES(5) Git Manual 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:
pattern attr1 attr2 ...
That is, a pattern followed by an attributes list, separated by
whitespaces. Leading and trailing whitespaces are ignored. Lines that
begin with # are ignored. Patterns that begin with a double quote are
quoted in C style. When the 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 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 pattern matches the path, a later line overrides an
earlier line. This overriding is done per attribute.
The rules by which the pattern matches paths are the same as in
.gitignore files (see gitignore(5)), with a few exceptions:
o negative patterns are forbidden
o patterns that match a directory do not recursively match paths
inside that directory (so using the trailing-slash path/ syntax is
pointless in an attributes file; use path/** instead)
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 up to the toplevel of the work tree (the further
the directory that contains .gitattributes is from the path in
question, the lower its precedence). Finally global and system-wide
files are considered (they have the lowest precedence).
When the .gitattributes file is missing from the work tree, the path in
the index is used as a fall-back. During checkout process,
.gitattributes in the index is used and then the file in the working
tree is used as a fall-back.
If you wish to affect only a single repository (i.e., to assign
attributes to files that are particular to one user's workflow for that
repository), 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. Attributes that should affect all repositories for a single user
should be placed in a file specified by the core.attributesFile
configuration option (see git-config(1)). Its default value is
$XDG_CONFIG_HOME/git/attributes. If $XDG_CONFIG_HOME is either not set
or empty, $HOME/.config/git/attributes is used instead. Attributes for
all users on a system should be placed in the
$(prefix)/etc/gitattributes file.
Sometimes you would need to override a 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 switch, 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.
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
setting core.autocrlf to true or input overrides core.eol (see the
definitions of those options in git-config(1)).
Set
Setting the text attribute on a path enables end-of-line
normalization and marks the path as a text file. End-of-line
conversion takes place without guessing the content type.
Unset
Unsetting the text attribute on a path tells Git not to attempt
any end-of-line conversion upon checkin or checkout.
Set to string value "auto"
When text is set to "auto", the path is marked for automatic
end-of-line conversion. If Git decides that the content is
text, its line endings are converted to LF on checkin. When the
file has been committed with CRLF, no conversion is done.
Unspecified
If the text attribute is unspecified, Git uses the
core.autocrlf configuration variable to determine if the file
should be converted.
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. Note that
setting this attribute on paths which are in the index with CRLF
line endings may make the paths to be considered dirty. Adding the
path to the index again will normalize the line endings in the
index.
Set to string value "crlf"
This setting forces Git to normalize line endings for this file
on checkin and convert them to CRLF when the file is checked
out.
Set to string value "lf"
This setting forces Git to normalize line endings to LF on
checkin and prevents conversion to CRLF when the file is
checked out.
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
Note
When text=auto conversion is enabled in a cross-platform
project using push and pull to a central repository the text
files containing CRLFs should be normalized.
From a clean working directory:
$ echo "* text=auto" >.gitattributes
$ git add --renormalize .
$ git status # Show files that will be normalized
$ 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...
o git add itself does not touch the files in the work tree, the
next checkout would, so the safety triggers;
o 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;
o 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.
working-tree-encoding
Git recognizes files encoded in ASCII or one of its supersets (e.g.
UTF-8, ISO-8859-1, ...) as text files. Files encoded in certain
other encodings (e.g. UTF-16) are interpreted as binary and
consequently built-in Git text processing tools (e.g. git diff) as
well as most Git web front ends do not visualize the contents of
these files by default.
In these cases you can tell Git the encoding of a file in the
working directory with the working-tree-encoding attribute. If a
file with this attribute is added to Git, then Git re-encodes the
content from the specified encoding to UTF-8. Finally, Git stores
the UTF-8 encoded content in its internal data structure (called
"the index"). On checkout the content is re-encoded back to the
specified encoding.
Please note that using the working-tree-encoding attribute may have
a number of pitfalls:
o Alternative Git implementations (e.g. JGit or libgit2) and
older Git versions (as of March 2018) do not support the
working-tree-encoding attribute. If you decide to use the
working-tree-encoding attribute in your repository, then it is
strongly recommended to ensure that all clients working with
the repository support it.
For example, Microsoft Visual Studio resources files (*.rc) or
PowerShell script files (*.ps1) are sometimes encoded in
UTF-16. If you declare *.ps1 as files as UTF-16 and you add
foo.ps1 with a working-tree-encoding enabled Git client, then
foo.ps1 will be stored as UTF-8 internally. A client without
working-tree-encoding support will checkout foo.ps1 as UTF-8
encoded file. This will typically cause trouble for the users
of this file.
If a Git client that does not support the working-tree-encoding
attribute adds a new file bar.ps1, then bar.ps1 will be stored
"as-is" internally (in this example probably as UTF-16). A
client with working-tree-encoding support will interpret the
internal contents as UTF-8 and try to convert it to UTF-16 on
checkout. That operation will fail and cause an error.
o Reencoding content to non-UTF encodings can cause errors as the
conversion might not be UTF-8 round trip safe. If you suspect
your encoding to not be round trip safe, then add it to
core.checkRoundtripEncoding to make Git check the round trip
encoding (see git-config(1)). SHIFT-JIS (Japanese character
set) is known to have round trip issues with UTF-8 and is
checked by default.
o Reencoding content requires resources that might slow down
certain Git operations (e.g git checkout or git add).
Use the working-tree-encoding attribute only if you cannot store a
file in UTF-8 encoding and if you want Git to be able to process
the content as text.
As an example, use the following attributes if your *.ps1 files are
UTF-16 encoded with byte order mark (BOM) and you want Git to
perform automatic line ending conversion based on your platform.
*.ps1 text working-tree-encoding=UTF-16
Use the following attributes if your *.ps1 files are UTF-16 little
endian encoded without BOM and you want Git to use Windows line
endings in the working directory (use UTF-16LE-BOM instead of
UTF-16LE if you want UTF-16 little endian with BOM). Please note,
it is highly recommended to explicitly define the line endings with
eol if the working-tree-encoding attribute is used to avoid
ambiguity.
*.ps1 text working-tree-encoding=UTF-16LE eol=CRLF
You can get a list of all available encodings on your platform with
the following command:
iconv --list
If you do not know the encoding of a file, then you can use the
file command to guess the encoding:
file foo.ps1
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.
Note: Whenever the clean filter is changed, the repo should be
renormalized: $ git add --renormalize .
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 the long-running process
protocol (described in
technical/long-running-process-protocol.txt).
When Git encounters the first file that needs to be cleaned or
smudged, it starts the filter and performs the handshake. In the
handshake, the welcome message sent by Git is "git-filter-client",
only version 2 is supported, and the supported capabilities are
"clean", "smudge", and "delay".
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.
Delay
If the filter supports the "delay" capability, then Git can send
the flag "can-delay" after the filter command and pathname. This
flag denotes that the filter can delay filtering the current blob
(e.g. to compensate network latencies) by responding with no
content but with the status "delayed" and a flush packet.
packet: git> command=smudge
packet: git> pathname=path/testfile.dat
packet: git> can-delay=1
packet: git> 0000
packet: git> CONTENT
packet: git> 0000
packet: git< status=delayed
packet: git< 0000
If the filter supports the "delay" capability then it must support
the "list_available_blobs" command. If Git sends this command, then
the filter is expected to return a list of pathnames representing
blobs that have been delayed earlier and are now available. The
list must be terminated with a flush packet followed by a "success"
status that is also terminated with a flush packet. If no blobs for
the delayed paths are available, yet, then the filter is expected
to block the response until at least one blob becomes available.
The filter can tell Git that it has no more delayed blobs by
sending an empty list. As soon as the filter responds with an empty
list, Git stops asking. All blobs that Git has not received at this
point are considered missing and will result in an error.
packet: git> command=list_available_blobs
packet: git> 0000
packet: git< pathname=path/testfile.dat
packet: git< pathname=path/otherfile.dat
packet: git< 0000
packet: git< status=success
packet: git< 0000
After Git received the pathnames, it will request the corresponding
blobs again. These requests contain a pathname and an empty content
section. The filter is expected to respond with the smudged content
in the usual way as explained above.
packet: git> command=smudge
packet: git> pathname=path/testfile.dat
packet: git> 0000
packet: git> 0000 # empty content!
packet: git< status=success
packet: git< 0000
packet: git< SMUDGED_CONTENT
packet: git< 0000
packet: git< 0000 # empty list, keep "status=success" unchanged!
Example
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.
Generating diff text
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.
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 (or a binary patch, if binary patches are
enabled).
Unspecified
A path to which the diff attribute is unspecified first gets
its contents inspected, and if it looks like text and is
smaller than core.bigFileThreshold, it is treated as text.
Otherwise it would generate Binary files differ.
String
Diff is shown using the specified diff driver. Each driver may
specify one or more options, as described in the following
section. The options for the diff driver "foo" are defined by
the configuration variables in the "diff.foo" section of the
Git config file.
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:
o ada suitable for source code in the Ada language.
o bibtex suitable for files with BibTeX coded references.
o cpp suitable for source code in the C and C++ languages.
o csharp suitable for source code in the C# language.
o css suitable for cascading style sheets.
o dts suitable for devicetree (DTS) files.
o elixir suitable for source code in the Elixir language.
o fortran suitable for source code in the Fortran language.
o fountain suitable for Fountain documents.
o golang suitable for source code in the Go language.
o html suitable for HTML/XHTML documents.
o java suitable for source code in the Java language.
o markdown suitable for Markdown documents.
o matlab suitable for source code in the MATLAB and Octave
languages.
o objc suitable for source code in the Objective-C language.
o pascal suitable for source code in the Pascal/Delphi language.
o perl suitable for source code in the Perl language.
o php suitable for source code in the PHP language.
o python suitable for source code in the Python language.
o ruby suitable for source code in the Ruby language.
o rust suitable for source code in the Rust language.
o tex suitable for source code for LaTeX documents.
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
Note
The text conversion is generally a one-way conversion; in this
example, we lose the actual image contents and focus just on
the text data. This means that diffs generated by textconv are
not suitable for applying. For this reason, only git diff and
the git log family of commands (i.e., log, whatchanged, show)
will perform text conversion. git format-patch will never
generate this output. If you want to send somebody a
text-converted diff of a binary file (e.g., because it quickly
conveys the changes you have made), you should generate it
separately and send it as a comment in addition to the usual
binary diff that you might send.
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:
1. Ease of use. It is often much simpler to write a binary to text
transformation than it is to perform your own diff. In many
cases, existing programs can be used as textconv filters (e.g.,
exif, odt2txt).
2. Git diff features. By performing only the transformation step
yourself, you can still utilize many of Git's diff features,
including colorization, word-diff, and combined diffs for
merges.
3. Caching. Textconv caching can speed up repeated diffs, such as
those you might trigger by running git log -p.
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
Performing a three-way merge
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.
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 do not have a well-defined merge
semantics.
Unspecified
By default, this uses the same built-in 3-way merge driver as
is the case when the merge attribute is set. However, the
merge.default configuration variable can name different merge
driver to be used with paths for 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 %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
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.
The tab width is taken from the value of the core.whitespace
configuration variable.
Unset
Do not notice anything as error.
Unspecified
Use the value of the 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 the core.whitespace configuration
variable.
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
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.
Packing objects
delta
Delta compression will not be attempted for blobs for paths with
the attribute delta set to false.
Viewing files in GUI tools
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)).
USING MACRO ATTRIBUTES
You do not want any end-of-line conversions applied to, nor textual
diffs produced for, any binary file you track. You would need to
specify e.g.
*.jpg -text -diff
but that may become cumbersome, when you have many attributes. Using
macro attributes, you can define an attribute that, when set, also sets
or unsets a number of other attributes at the same time. The system
knows a built-in macro attribute, binary:
*.jpg binary
Setting the "binary" attribute also unsets the "text" and "diff"
attributes as above. Note that macro attributes can only be "Set",
though setting one might have the effect of setting or unsetting other
attributes or even returning other attributes to the "Unspecified"
state.
DEFINING MACRO ATTRIBUTES
Custom macro attributes can be defined only in top-level gitattributes
files ($GIT_DIR/info/attributes, the .gitattributes file at the top
level of the working tree, or the global or system-wide gitattributes
files), not in .gitattributes files in working tree subdirectories. The
built-in macro attribute "binary" is equivalent to:
[attr]binary -diff -merge -text
EXAMPLES
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
SEE ALSO
git-check-attr(1).
GIT
Part of the git(1) suite
Git 2.27.0 06/01/2020 GITATTRIBUTES(5)