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diff --git a/Documentation/diff-format.txt b/Documentation/diff-format.txt new file mode 100644 index 0000000000..001503205b --- /dev/null +++ b/Documentation/diff-format.txt @@ -0,0 +1,242 @@ +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. + +diff format for merges +---------------------- + +"git-diff-tree" and "git-diff-files" can take '-c' or '--cc' option +to generate diff output also for merge commits. The output differs +from the format described above in the following way: + +. there is a colon for each parent +. there are more "src" modes and "src" sha1 +. status is concatenated status characters for each parent +. no optional "score" number +. single path, only for "dst" + +Example: + +------------------------------------------------ +::100644 100644 100644 fabadb8... cc95eb0... 4866510... MM describe.c +------------------------------------------------ + +Note that 'combined diff' lists only files which were modified from +all parents. + + +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. You can customize the creation +of such patches via the GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS +environment variables. + +What the -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, double quote and backslash characters in pathnames + are represented as `\t`, `\n`, `\"` and `\\`, respectively. + If there is need for such substitution then the whole + pathname is put in double quotes. + +The similarity index is the percentage of unchanged lines, and +the dissimilarity index is the percentage of changed lines. It +is a rounded down integer, followed by a percent sign. The +similarity index value of 100% is thus reserved for two equal +files, while 100% dissimilarity means that no line from the old +file made it into the new one. + + +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 +index fabadb8,cc95eb0..4866510 +--- a/describe.c ++++ b/describe.c +@@@ -98,20 -98,12 +98,20 @@@ + 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; + struct commit_list *list; + static int initialized = 0; + struct commit_name *n; + + + if (get_sha1(arg, sha1) < 0) + + usage(describe_usage); + + cmit = lookup_commit_reference(sha1); + + if (!cmit) + + usage(describe_usage); + + + if (!initialized) { + initialized = 1; + for_each_ref(get_name); +------------ + +1. It is preceded with a "git diff" header, that looks like + this (when '-c' option is used): + + diff --combined file ++ +or like this (when '--cc' option is used): + + diff --c file + +2. It is followed by one or more extended header lines + (this example shows a merge with two parents): + + index <hash>,<hash>..<hash> + mode <mode>,<mode>..<mode> + new file mode <mode> + deleted file mode <mode>,<mode> ++ +The `mode <mode>,<mode>..<mode>` line appears only if at least one of +the <mode> is different from the rest. Extended headers with +information about detected contents movement (renames and +copying detection) are designed to work with diff of two +<tree-ish> and are not used by combined diff format. + +3. It is followed by two-line from-file/to-file header + + --- a/file + +++ b/file ++ +Similar to two-line header for traditional 'unified' diff +format, `/dev/null` is used to signal created or deleted +files. + +4. Chunk header format is modified to prevent people from + accidentally feeding it to `patch -p1`. Combined diff format + was created for review of merge commit changes, and was not + meant for apply. The change is similar to the change in the + extended 'index' header: + + @@@ <from-file-range> <from-file-range> <to-file-range> @@@ ++ +There are (number of parents + 1) `@` characters in the chunk +header for combined diff format. + +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 result. A `+` character +in the column N means that the line appears in the last file, +and fileN does not have that line (in other words, the line was +added, from the point of view of that parent). + +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"). |