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+The output format from "git-diff-index", "git-diff-tree",
+"git-diff-files" and "git diff --raw" 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.
+
+Possible status letters are:
+
+- A: addition of a file
+- C: copy of a file into a new one
+- D: deletion of a file
+- M: modification of the contents or mode of a file
+- R: renaming of a file
+- T: change in the type of the file
+- U: file is unmerged (you must complete the merge before it can
+be committed)
+- X: "unknown" change type (most probably a bug, please report it)
+
+Status letters C and M are always followed by a score (denoting the
+percentage of similarity between the source and target of the move or
+copy), and are the only ones to be so.
+
+<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", "git-diff-files" and "git-diff --raw"
+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.
+
+
+include::diff-generate-patch.txt[]
+
+
+other diff formats
+------------------
+
+The `--summary` option describes newly added, deleted, renamed and
+copied files.  The `--stat` option adds diffstat(1) graph to the
+output.  These options can be combined with other options, such as
+`-p`, and are meant for human consumption.
+
+When showing a change that involves a rename or a copy, `--stat` output
+formats the pathnames compactly by combining common prefix and suffix of
+the pathnames.  For example, a change that moves `arch/i386/Makefile` to
+`arch/x86/Makefile` while modifying 4 lines will be shown like this:
+
+------------------------------------
+arch/{i386 => x86}/Makefile    |   4 +--
+------------------------------------
+
+The `--numstat` option gives the diffstat(1) information but is designed
+for easier machine consumption.  An entry in `--numstat` output looks
+like this:
+
+----------------------------------------
+1	2	README
+3	1	arch/{i386 => x86}/Makefile
+----------------------------------------
+
+That is, from left to right:
+
+. the number of added lines;
+. a tab;
+. the number of deleted lines;
+. a tab;
+. pathname (possibly with rename/copy information);
+. a newline.
+
+When `-z` output option is in effect, the output is formatted this way:
+
+----------------------------------------
+1	2	README NUL
+3	1	NUL arch/i386/Makefile NUL arch/x86/Makefile NUL
+----------------------------------------
+
+That is:
+
+. the number of added lines;
+. a tab;
+. the number of deleted lines;
+. a tab;
+. a NUL (only exists if renamed/copied);
+. pathname in preimage;
+. a NUL (only exists if renamed/copied);
+. pathname in postimage (only exists if renamed/copied);
+. a NUL.
+
+The extra `NUL` before the preimage path in renamed case is to allow
+scripts that read the output to tell if the current record being read is
+a single-path record or a rename/copy record without reading ahead.
+After reading added and deleted lines, reading up to `NUL` would yield
+the pathname, but if that is `NUL`, the record will show two paths.