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diff --git a/Documentation/diff-format.txt b/Documentation/diff-format.txt new file mode 100644 index 0000000000..617d8f526f --- /dev/null +++ b/Documentation/diff-format.txt @@ -0,0 +1,197 @@ +The output format from "git-diff-index", "git-diff-tree" and +"git-diff-files" are very similar. + +These commands all compare two sets of things; what is +compared differs: + +git-diff-index <tree-ish>:: + compares the <tree-ish> and the files on the filesystem. + +git-diff-index --cached <tree-ish>:: + compares the <tree-ish> and the index. + +git-diff-tree [-r] <tree-ish-1> <tree-ish-2> [<pattern>...]:: + compares the trees named by the two arguments. + +git-diff-files [<pattern>...]:: + compares the index and the files on the filesystem. + + +An output line is formatted this way: + +------------------------------------------------ +in-place edit :100644 100644 bcd1234... 0123456... M file0 +copy-edit :100644 100644 abcd123... 1234567... C68 file1 file2 +rename-edit :100644 100644 abcd123... 1234567... R86 file1 file3 +create :000000 100644 0000000... 1234567... A file4 +delete :100644 000000 1234567... 0000000... D file5 +unmerged :000000 000000 0000000... 0000000... U file6 +------------------------------------------------ + +That is, from the left to the right: + +. a colon. +. mode for "src"; 000000 if creation or unmerged. +. a space. +. mode for "dst"; 000000 if deletion or unmerged. +. a space. +. sha1 for "src"; 0\{40\} if creation or unmerged. +. a space. +. sha1 for "dst"; 0\{40\} if creation, unmerged or "look at work tree". +. a space. +. status, followed by optional "score" number. +. a tab or a NUL when '-z' option is used. +. path for "src" +. a tab or a NUL when '-z' option is used; only exists for C or R. +. path for "dst"; only exists for C or R. +. an LF or a NUL when '-z' option is used, to terminate the record. + +<sha1> is shown as all 0's if a file is new on the filesystem +and it is out of sync with the index. + +Example: + +------------------------------------------------ +:100644 100644 5be4a4...... 000000...... M file.c +------------------------------------------------ + +When `-z` option is not used, TAB, LF, and backslash characters +in pathnames are represented as `\t`, `\n`, and `\\`, +respectively. + + +Generating patches with -p +-------------------------- + +When "git-diff-index", "git-diff-tree", or "git-diff-files" are run +with a '-p' option, they do not produce the output described above; +instead they produce a patch file. + +The patch generation can be customized at two levels. + +1. When the environment variable 'GIT_EXTERNAL_DIFF' is not set, + these commands internally invoke "diff" like this: + + diff -L a/<path> -L b/<path> -pu <old> <new> ++ +For added files, `/dev/null` is used for <old>. For removed +files, `/dev/null` is used for <new> ++ +The "diff" formatting options can be customized via the +environment variable 'GIT_DIFF_OPTS'. For example, if you +prefer context diff: + + GIT_DIFF_OPTS=-c git-diff-index -p HEAD + + +2. When the environment variable 'GIT_EXTERNAL_DIFF' is set, the + program named by it is called, instead of the diff invocation + described above. ++ +For a path that is added, removed, or modified, +'GIT_EXTERNAL_DIFF' is called with 7 parameters: + + path old-file old-hex old-mode new-file new-hex new-mode ++ +where: + + <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the + contents of <old|new>, + <old|new>-hex:: are the 40-hexdigit SHA1 hashes, + <old|new>-mode:: are the octal representation of the file modes. + ++ +The file parameters can point at the user's working file +(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file` +when a new file is added), or a temporary file (e.g. `old-file` in the +index). 'GIT_EXTERNAL_DIFF' should not worry about unlinking the +temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits. + +For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1 +parameter, <path>. + + +git specific extension to diff format +------------------------------------- + +What -p option produces is slightly different from the +traditional diff format. + +1. It is preceded with a "git diff" header, that looks like + this: + + diff --git a/file1 b/file2 ++ +The `a/` and `b/` filenames are the same unless rename/copy is +involved. Especially, even for a creation or a deletion, +`/dev/null` is _not_ used in place of `a/` or `b/` filenames. ++ +When rename/copy is involved, `file1` and `file2` show the +name of the source file of the rename/copy and the name of +the file that rename/copy produces, respectively. + +2. It is followed by one or more extended header lines: + + old mode <mode> + new mode <mode> + deleted file mode <mode> + new file mode <mode> + copy from <path> + copy to <path> + rename from <path> + rename to <path> + similarity index <number> + dissimilarity index <number> + index <hash>..<hash> <mode> + +3. TAB, LF, and backslash characters in pathnames are + represented as `\t`, `\n`, and `\\`, respectively. + + +combined diff format +-------------------- + +git-diff-tree and git-diff-files can take '-c' or '--cc' option +to produce 'combined diff', which looks like this: + +------------ +diff --combined describe.c +@@@ +98,7 @@@ + return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1; + } + +- static void describe(char *arg) + -static void describe(struct commit *cmit, int last_one) +++static void describe(char *arg, int last_one) + { + + unsigned char sha1[20]; + + struct commit *cmit; +------------ + +Unlike the traditional 'unified' diff format, which shows two +files A and B with a single column that has `-` (minus -- +appears in A but removed in B), `+` (plus -- missing in A but +added to B), or ` ` (space -- unchanged) prefix, this format +compares two or more files file1, file2,... with one file X, and +shows how X differs from each of fileN. One column for each of +fileN is prepended to the output line to note how X's line is +different from it. + +A `-` character in the column N means that the line appears in +fileN but it does not appear in the last file. A `+` character +in the column N means that the line appears in the last file, +and fileN does not have that line. + +In the above example output, the function signature was changed +from both files (hence two `-` removals from both file1 and +file2, plus `++` to mean one line that was added does not appear +in either file1 nor file2). Also two other lines are the same +from file1 but do not appear in file2 (hence prefixed with ` +`). + +When shown by `git diff-tree -c`, it compares the parents of a +merge commit with the merge result (i.e. file1..fileN are the +parents). When shown by `git diff-files -c`, it compares the +two unresolved merge parents with the working tree file +(i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka +"their version"). + |