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diff --git a/third_party/git/Documentation/gitattributes.txt b/third_party/git/Documentation/gitattributes.txt new file mode 100644 index 000000000000..508fe713c4cf --- /dev/null +++ b/third_party/git/Documentation/gitattributes.txt @@ -0,0 +1,1298 @@ +gitattributes(5) +================ + +NAME +---- +gitattributes - Defining attributes per path + +SYNOPSIS +-------- +$GIT_DIR/info/attributes, .gitattributes + + +DESCRIPTION +----------- + +A `gitattributes` file is a simple text file that gives +`attributes` to pathnames. + +Each line in `gitattributes` file is of form: + + pattern attr1 attr2 ... + +That is, a pattern followed by an attributes list, +separated by whitespaces. Leading and trailing whitespaces are +ignored. Lines that begin with '#' are ignored. Patterns +that begin with a double quote are quoted in C style. +When the pattern matches the path in question, the attributes +listed on the line are given to the path. + +Each attribute can be in one of these states for a given path: + +Set:: + + The path has the attribute with special value "true"; + this is specified by listing only the name of the + attribute in the attribute list. + +Unset:: + + The path has the attribute with special value "false"; + this is specified by listing the name of the attribute + prefixed with a dash `-` in the attribute list. + +Set to a value:: + + The path has the attribute with specified string value; + this is specified by listing the name of the attribute + followed by an equal sign `=` and its value in the + attribute list. + +Unspecified:: + + No pattern matches the path, and nothing says if + the path has or does not have the attribute, the + attribute for the path is said to be Unspecified. + +When more than one pattern matches the path, a later line +overrides an earlier line. This overriding is done per +attribute. + +The rules by which the pattern matches paths are the same as in +`.gitignore` files (see linkgit:gitignore[5]), with a few exceptions: + + - negative patterns are forbidden + + - patterns that match a directory do not recursively match paths + inside that directory (so using the trailing-slash `path/` syntax is + pointless in an attributes file; use `path/**` instead) + +When deciding what attributes are assigned to a path, Git +consults `$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 linkgit: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 +linkgit: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... + +- '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. + + +`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: + +- 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. + +- 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 linkgit:git-config[1]). SHIFT-JIS (Japanese character + set) is known to have round trip issues with UTF-8 and is checked by + default. + +- 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 linkgit: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 linkgit: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: + +- `ada` suitable for source code in the Ada language. + +- `bibtex` suitable for files with BibTeX coded references. + +- `cpp` suitable for source code in the C and C++ languages. + +- `csharp` suitable for source code in the C# language. + +- `css` suitable for cascading style sheets. + +- `dts` suitable for devicetree (DTS) files. + +- `elixir` suitable for source code in the Elixir language. + +- `fortran` suitable for source code in the Fortran language. + +- `fountain` suitable for Fountain documents. + +- `golang` suitable for source code in the Go language. + +- `html` suitable for HTML/XHTML documents. + +- `java` suitable for source code in the Java language. + +- `matlab` suitable for source code in the MATLAB and Octave languages. + +- `objc` suitable for source code in the Objective-C language. + +- `pascal` suitable for source code in the Pascal/Delphi language. + +- `perl` suitable for source code in the Perl language. + +- `php` suitable for source code in the PHP language. + +- `python` suitable for source code in the Python language. + +- `ruby` suitable for source code in the Ruby language. + +- `rust` suitable for source code in the Rust language. + +- `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 linkgit: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 +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$` will be replaced by the +commit hash. + + +Packing objects +~~~~~~~~~~~~~~~ + +`delta` +^^^^^^^ + +Delta compression will not be attempted for blobs for paths with the +attribute `delta` set to false. + + +Viewing files in GUI tools +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +`encoding` +^^^^^^^^^^ + +The value of this attribute specifies the character encoding that should +be used by GUI tools (e.g. linkgit:gitk[1] and linkgit:git-gui[1]) to +display the contents of the relevant file. Note that due to performance +considerations linkgit:gitk[1] does not use this attribute unless you +manually enable per-file encodings in its options. + +If this attribute is not set or has an invalid value, the value of the +`gui.encoding` configuration variable is used instead +(See linkgit:git-config[1]). + + +USING MACRO ATTRIBUTES +---------------------- + +You do not want any end-of-line conversions applied to, nor textual diffs +produced for, any binary file you track. You would need to specify e.g. + +------------ +*.jpg -text -diff +------------ + +but that may become cumbersome, when you have many attributes. Using +macro attributes, you can define an attribute that, when set, also +sets or unsets a number of other attributes at the same time. The +system knows a built-in macro attribute, `binary`: + +------------ +*.jpg binary +------------ + +Setting the "binary" attribute also unsets the "text" and "diff" +attributes as above. Note that macro attributes can only be "Set", +though setting one might have the effect of setting or unsetting other +attributes or even returning other attributes to the "Unspecified" +state. + + +DEFINING MACRO ATTRIBUTES +------------------------- + +Custom macro attributes can be defined only in top-level gitattributes +files (`$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 +-------- +linkgit:git-check-attr[1]. + +GIT +--- +Part of the linkgit:git[1] suite |