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.
+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.
-The patch generation can be customized at two levels.
+What the -p option produces is slightly different from the traditional
+diff format.
-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 preceeded with a "git diff" header, that looks like
+1. It is preceded with a "git diff" header, that looks like
this:
- diff --git a/file1 b/file2
+ 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,
dissimilarity index <number>
index <hash>..<hash> <mode>
-3. TAB, LF, and backslash characters in pathnames are
- represented as `\t`, `\n`, and `\\`, respectively.
+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.
+
+
+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 diferent 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").
+