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diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt new file mode 100644 index 0000000000..810df07217 --- /dev/null +++ b/Documentation/gitattributes.txt @@ -0,0 +1,426 @@ +gitattributes(5) +================ + +NAME +---- +gitattributes - defining attributes per path + +SYNOPSIS +-------- +$GIT_DIR/info/attributes, gitattributes + + +DESCRIPTION +----------- + +A `gitattributes` file is a simple text file that gives +`attributes` to pathnames. + +Each line in `gitattributes` file is of form: + + glob attr1 attr2 ... + +That is, a glob pattern followed by an attributes list, +separated by whitespaces. When the glob pattern matches the +path in question, the attributes listed on the line are given to +the path. + +Each attribute can be in one of these states for a given path: + +Set:: + + The path has the attribute with special value "true"; + this is specified by listing only the name of the + attribute in the attribute list. + +Unset:: + + The path has the attribute with special value "false"; + this is specified by listing the name of the attribute + prefixed with a dash `-` in the attribute list. + +Set to a value:: + + The path has the attribute with specified string value; + this is specified by listing the name of the attribute + followed by an equal sign `=` and its value in the + attribute list. + +Unspecified:: + + No glob pattern matches the path, and nothing says if + the path has or does not have the attribute, the + attribute for the path is said to be Unspecified. + +When more than one glob pattern matches the path, a later line +overrides an earlier line. This overriding is done per +attribute. + +When deciding what attributes are assigned to a path, git +consults `$GIT_DIR/info/attributes` file (which has the highest +precedence), `.gitattributes` file in the same directory as the +path in question, and its parent directories (the further the +directory that contains `.gitattributes` is from the path in +question, the lower its precedence). + +Sometimes you would need to override an setting of an attribute +for a path to `unspecified` state. This can be done by listing +the name of the attribute prefixed with an exclamation point `!`. + + +EFFECTS +------- + +Certain operations by git can be influenced by assigning +particular attributes to a path. Currently, the following +operations are attributes-aware. + +Checking-out and checking-in +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +These attributes affect how the contents stored in the +repository are copied to the working tree files when commands +such as `git checkout` and `git merge` run. They also affect how +git stores the contents you prepare in the working tree in the +repository upon `git add` and `git commit`. + +`crlf` +^^^^^^ + +This attribute controls the line-ending convention. + +Set:: + + Setting the `crlf` attribute on a path is meant to mark + the path as a "text" file. 'core.autocrlf' conversion + takes place without guessing the content type by + inspection. + +Unset:: + + Unsetting the `crlf` attribute on a path is meant to + mark the path as a "binary" file. The path never goes + through line endings conversion upon checkin/checkout. + +Unspecified:: + + Unspecified `crlf` attribute tells git to apply the + `core.autocrlf` conversion when the file content looks + like text. + +Set to string value "input":: + + This is similar to setting the attribute to `true`, but + also forces git to act as if `core.autocrlf` is set to + `input` for the path. + +Any other value set to `crlf` attribute is ignored and git acts +as if the attribute is left unspecified. + + +The `core.autocrlf` conversion +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If the configuration variable `core.autocrlf` is false, no +conversion is done. + +When `core.autocrlf` is true, it means that the platform wants +CRLF line endings for files in the working tree, and you want to +convert them back to the normal LF line endings when checking +in to the repository. + +When `core.autocrlf` is set to "input", line endings are +converted to LF upon checkin, but there is no conversion done +upon checkout. + + +`ident` +^^^^^^^ + +When the attribute `ident` is set to a path, git replaces +`$Id$` in the blob object with `$Id:`, followed by +40-character hexadecimal blob object name, followed by a dollar +sign `$` upon checkout. Any byte sequence that begins with +`$Id:` and ends with `$` in the worktree file is replaced +with `$Id$` upon check-in. + + +Interaction between checkin/checkout attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In the check-in codepath, the worktree file is first converted +with `ident` (if specified), and then with `crlf` (again, if +specified and applicable). + +In the check-out codepath, the blob content is first converted +with `crlf`, and then `ident`. + + +`filter` +^^^^^^^^ + +A `filter` attribute can be set to a string value. This names +filter driver specified in the configuration. + +A filter driver consists of `clean` command and `smudge` +command, either of which can be left unspecified. Upon +checkout, when `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, `clean` command +is used to convert the contents of worktree file upon checkin. + +Missing filter driver definition in the config is not an error +but makes the filter a no-op passthru. + +The content filtering is done to massage the content into a +shape that is more convenient for the platform, filesystem, and +the user to use. The keyword here is "more convenient" and not +"turning something unusable into usable". In other words, it is +"hanging yourself because we gave you a long rope" if your +project uses filtering mechanism in such a way that it makes +your project unusable unless the checkout is done with a +specific filter in effect. + + +Interaction between checkin/checkout attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In the check-in codepath, the worktree file is first converted +with `filter` driver (if specified and corresponding driver +defined), then the result is processed with `ident` (if +specified), and then finally with `crlf` (again, if specified +and applicable). + +In the check-out codepath, the blob content is first converted +with `crlf`, and then `ident` and fed to `filter`. + + +Generating diff text +~~~~~~~~~~~~~~~~~~~~ + +The attribute `diff` affects if `git diff` generates textual +patch for the path or just says `Binary files differ`. It also +can affect what line is shown on the hunk header `@@ -k,l +n,m @@` +line. + +Set:: + + A path to which the `diff` attribute is set is treated + as text, even when they contain byte values that + normally never appear in text files, such as NUL. + +Unset:: + + A path to which the `diff` attribute is unset will + generate `Binary files differ`. + +Unspecified:: + + A path to which the `diff` attribute is unspecified + first gets its contents inspected, and if it looks like + text, it is treated as text. Otherwise it would + generate `Binary files differ`. + +String:: + + Diff is shown using the specified custom diff driver. + The driver program is given its input using the same + calling convention as used for GIT_EXTERNAL_DIFF + program. This name is also used for custom hunk header + selection. + + +Defining a custom diff driver +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The definition of a diff driver is done in `gitconfig`, not +`gitattributes` file, so strictly speaking this manual page is a +wrong place to talk about it. However... + +To define a custom diff driver `jcdiff`, add a section to your +`$GIT_DIR/config` file (or `$HOME/.gitconfig` file) like this: + +---------------------------------------------------------------- +[diff "jcdiff"] + command = j-c-diff +---------------------------------------------------------------- + +When git needs to show you a diff for the path with `diff` +attribute set to `jcdiff`, it calls the command you specified +with the above configuration, i.e. `j-c-diff`, with 7 +parameters, just like `GIT_EXTERNAL_DIFF` program is called. +See gitlink:git[7] for details. + + +Defining a custom hunk-header +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Each group of changes (called "hunk") in the textual diff output +is prefixed with a line of the form: + + @@ -k,l +n,m @@ TEXT + +The text is called 'hunk header', and by default a line that +begins with an alphabet, an underscore or a dollar sign is used, +which matches what GNU `diff -p` output uses. This default +selection however is not suited for some contents, and you can +use customized pattern to make a selection. + +First in .gitattributes, you would assign the `diff` attribute +for paths. + +------------------------ +*.tex diff=tex +------------------------ + +Then, you would define "diff.tex.funcname" configuration to +specify a regular expression that matches a line that you would +want to appear as the hunk header, like this: + +------------------------ +[diff "tex"] + funcname = "^\\(\\\\\\(sub\\)*section{.*\\)$" +------------------------ + +Note. A single level of backslashes are eaten by the +configuration file parser, so you would need to double the +backslashes; the pattern above picks a line that begins with a +backslash, and zero or more occurences of `sub` followed by +`section` followed by open brace, to the end of line. + +There are a few built-in patterns to make this easier, and `tex` +is one of them, so you do not have to write the above in your +configuration file (you still need to enable this with the +attribute mechanism, via `.gitattributes`). Another built-in +pattern is defined for `java` that defines a pattern suitable +for program text in Java language. + + +Performing a three-way merge +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The attribute `merge` affects how three versions of a file is +merged when a file-level merge is necessary during `git merge`, +and other programs such as `git revert` and `git cherry-pick`. + +Set:: + + Built-in 3-way merge driver is used to merge the + contents in a way similar to `merge` command of `RCS` + suite. This is suitable for ordinary text files. + +Unset:: + + Take the version from the current branch as the + tentative merge result, and declare that the merge has + conflicts. This is suitable for binary files that does + not have a well-defined merge semantics. + +Unspecified:: + + By default, this uses the same built-in 3-way merge + driver as is the case the `merge` attribute is set. + However, `merge.default` configuration variable can name + different merge driver to be used for paths to which the + `merge` attribute is unspecified. + +String:: + + 3-way merge is performed using the specified custom + merge driver. The built-in 3-way merge driver can be + explicitly specified by asking for "text" driver; the + built-in "take the current branch" driver can be + requested with "binary". + + +Defining a custom merge driver +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The definition of a merge driver is done in `gitconfig` not +`gitattributes` file, so strictly speaking this manual page is a +wrong place to talk about it. However... + +To define a custom merge driver `filfre`, add a section to your +`$GIT_DIR/config` file (or `$HOME/.gitconfig` file) like this: + +---------------------------------------------------------------- +[merge "filfre"] + name = feel-free merge driver + driver = filfre %O %A %B + recursive = binary +---------------------------------------------------------------- + +The `merge.*.name` variable gives the driver a human-readable +name. + +The `merge.*.driver` variable's value is used to construct a +command to run to merge ancestor's version (`%O`), current +version (`%A`) and the other branches' version (`%B`). These +three tokens are replaced with the names of temporary files that +hold the contents of these versions when the command line is +built. + +The merge driver is expected to leave the result of the merge in +the file named with `%A` by overwriting it, and exit with zero +status if it managed to merge them cleanly, or non-zero if there +were conflicts. + +The `merge.*.recursive` variable specifies what other merge +driver to use when the merge driver is called for an internal +merge between common ancestors, when there are more than one. +When left unspecified, the driver itself is used for both +internal merge and the final merge. + + +EXAMPLE +------- + +If you have these three `gitattributes` file: + +---------------------------------------------------------------- +(in $GIT_DIR/info/attributes) + +a* foo !bar -baz + +(in .gitattributes) +abc foo bar baz + +(in t/.gitattributes) +ab* merge=filfre +abc -foo -bar +*.c frotz +---------------------------------------------------------------- + +the attributes given to path `t/abc` are computed as follows: + +1. By examining `t/.gitattributes` (which is in the same + diretory as the path in question), git finds that the first + line matches. `merge` attribute is set. It also finds that + the second line matches, and attributes `foo` and `bar` + are unset. + +2. Then it examines `.gitattributes` (which is in the parent + directory), and finds that the first line matches, but + `t/.gitattributes` file already decided how `merge`, `foo` + and `bar` attributes should be given to this path, so it + leaves `foo` and `bar` unset. Attribute `baz` is set. + +3. Finally it examines `$GIT_DIR/info/gitattributes`. This file + is used to override the in-tree settings. The first line is + a match, and `foo` is set, `bar` is reverted to unspecified + state, and `baz` is unset. + +As the result, the attributes assignement to `t/abc` becomes: + +---------------------------------------------------------------- +foo set to true +bar unspecified +baz set to false +merge set to string value "filfre" +frotz unspecified +---------------------------------------------------------------- + + +GIT +--- +Part of the gitlink:git[7] suite |