Git - diff-format Documentation (2023)

Raw output format

The raw 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 iscompared 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.

The "git-diff-tree" command begins its output by printing the hash ofwhat is being compared. After that, all the commands print one outputline per changed file.

An output line is formatted this way:

in-place edit :100644 100644 bcd1234 0123456 M file0copy-edit :100644 100644 abcd123 1234567 C68 file1 file2rename-edit :100644 100644 abcd123 1234567 R86 file1 file3create :000000 100644 0000000 1234567 A file4delete :100644 000000 1234567 0000000 D file5unmerged :000000 000000 0000000 0000000 U file6

That is, from the left to the right:

  1. a colon.

  2. mode for "src"; 000000 if creation or unmerged.

  3. a space.

  4. mode for "dst"; 000000 if deletion or unmerged.

  5. a space.

  6. sha1 for "src"; 0{40} if creation or unmerged.

  7. a space.

  8. sha1 for "dst"; 0{40} if deletion, unmerged or "work tree out of sync with the index".

  9. a space.

  10. status, followed by optional "score" number.

  11. a tab or a NUL when -z option is used.

  12. path for "src"

  13. a tab or a NUL when -z option is used; only exists for C or R.

  14. path for "dst"; only exists for C or R.

  15. 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 (regular file, symbolic link or submodule)

  • U: file is unmerged (you must complete the merge before it canbe committed)

  • X: "unknown" change type (most probably a bug, please report it)

Status letters C and R are always followed by a score (denoting thepercentage of similarity between the source and target of the move orcopy). Status letter M may be followed by a score (denoting thepercentage of dissimilarity) for file rewrites.

The sha1 for "dst" is shown as all 0’s if a file on the filesystemis out of sync with the index.


:100644 100644 5be4a4a 0000000 M file.c

Without the -z option, pathnames with "unusual" characters arequoted as explained for the configuration variable core.quotePath(see git-config[1]). Using -z the filename is outputverbatim and the line is terminated by a NUL byte.

diff format for merges

"git-diff-tree", "git-diff-files" and "git-diff --raw"can take -c or --cc optionto generate diff output also for merge commits. The output differsfrom the format described above in the following way:

  1. there is a colon for each parent

  2. there are more "src" modes and "src" sha1

  3. status is concatenated status characters for each parent

  4. no optional "score" number

  5. tab-separated pathname(s) of the file

For -c and --cc, only the destination or final path is shown evenif the file was renamed on any side of history. With--combined-all-paths, the name of the path in each parent is shownfollowed by the name of the path in the merge commit.

Examples for -c and --cc without --combined-all-paths:

::100644 100644 100644 fabadb8 cc95eb0 4866510 MMdesc.c::100755 100755 100755 52b7a2d 6d1ac04 d2ac7d7 100644 100644 e07d6c5 9042e82 ee91881 RRphooey.c

Examples when --combined-all-paths added to either -c or --cc:

::100644 100644 100644 fabadb8 cc95eb0 4866510 MMdesc.cdesc.cdesc.c::100755 100755 100755 52b7a2d 6d1ac04 d2ac7d7 100644 100644 e07d6c5 9042e82 ee91881 RRfooey.cfuey.cphooey.c

Note that combined diff lists only files which were modified fromall parents.

Generating patch text with -p

Runninggit-diff[1],git-log[1],git-show[1],git-diff-index[1],git-diff-tree[1], orgit-diff-files[1]with the -p option produces patch text.You can customize the creation of patch text via theGIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables(see git[1]), and the diff attribute (see gitattributes[5]).

What the -p option produces is slightly different from the traditionaldiff 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 isinvolved. Especially, even for a creation or a deletion,/dev/null is not used in place of the a/ or b/ filenames.

    When rename/copy is involved, file1 and file2 show thename of the source file of the rename/copy and the name ofthe 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>

    File modes are printed as 6-digit octal numbers including the file typeand file permission bits.

    Path names in extended headers do not include the a/ and b/ prefixes.

    The similarity index is the percentage of unchanged lines, andthe dissimilarity index is the percentage of changed lines. Itis a rounded down integer, followed by a percent sign. Thesimilarity index value of 100% is thus reserved for two equalfiles, while 100% dissimilarity means that no line from the oldfile made it into the new one.

    The index line includes the blob object names before and after the change.The <mode> is included if the file mode does not change; otherwise,separate lines indicate the old and the new mode.

  3. Pathnames with "unusual" characters are quoted as explained forthe configuration variable core.quotePath (seegit-config[1]).

  4. All the file1 files in the output refer to files before thecommit, and all the file2 files refer to files after the commit.It is incorrect to apply each change to each file sequentially. Forexample, this patch will swap a and b:

    diff --git a/a b/brename from arename to bdiff --git a/b b/arename from brename to a
  5. Hunk headers mention the name of the function to which the hunkapplies. See "Defining a custom hunk-header" ingitattributes[5] for details of how to tailor to this tospecific languages.

Combined diff format

Any diff-generating command can take the -c or --cc option toproduce a combined diff when showing a merge. This is the defaultformat when showing merges with git-diff[1] orgit-show[1]. Note also that you can give suitable--diff-merges option to any of these commands to force generation ofdiffs in specific format.

A "combined diff" format looks like this:

diff --combined describe.cindex 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 likethis (when the -c option is used):

    diff --combined file

    or like this (when the --cc option is used):

    diff --cc 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 ofthe <mode> is different from the rest. Extended headers withinformation about detected contents movement (renames andcopying 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 diffformat, /dev/null is used to signal created or deletedfiles.

    However, if the --combined-all-paths option is provided, instead of atwo-line from-file/to-file you get a N+1 line from-file/to-file header,where N is the number of parents in the merge commit

    --- a/file--- a/file--- a/file+++ b/file

    This extended format can be useful if rename or copy detection isactive, to allow you to see the original name of the file in differentparents.

  4. Chunk header format is modified to prevent people fromaccidentally feeding it to patch -p1. Combined diff formatwas created for review of merge commit changes, and was notmeant to be applied. The change is similar to the change in theextended index header:

    @@@ <from-file-range> <from-file-range> <to-file-range> @@@

    There are (number of parents + 1) @ characters in the chunkheader for combined diff format.

Unlike the traditional unified diff format, which shows twofiles A and B with a single column that has - (minus — appears in A but removed in B), + (plus — missing in A butadded to B), or " " (space — unchanged) prefix, this formatcompares two or more files file1, file2,…​ with one file X, andshows how X differs from each of fileN. One column for each offileN is prepended to the output line to note how X’s line isdifferent from it.

A - character in the column N means that the line appears infileN but it does not appear in the result. A + characterin the column N means that the line appears in the result,and fileN does not have that line (in other words, the line wasadded, from the point of view of that parent).

In the above example output, the function signature was changedfrom both files (hence two - removals from both file1 andfile2, plus ++ to mean one line that was added does not appearin either file1 or file2). Also eight other lines are the samefrom file1 but do not appear in file2 (hence prefixed with +).

When shown by git diff-tree -c, it compares the parents of amerge commit with the merge result (i.e. file1..fileN are theparents). When shown by git diff-files -c, it compares thetwo unresolved merge parents with the working tree file(i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka"their version").

other diff formats

The --summary option describes newly added, deleted, renamed andcopied files. The --stat option adds diffstat(1) graph to theoutput. 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 outputformats the pathnames compactly by combining common prefix and suffix ofthe pathnames. For example, a change that moves arch/i386/Makefile toarch/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 designedfor easier machine consumption. An entry in --numstat output lookslike this:

12README31arch/{i386 => x86}/Makefile

That is, from left to right:

  1. the number of added lines;

  2. a tab;

  3. the number of deleted lines;

  4. a tab;

  5. pathname (possibly with rename/copy information);

  6. a newline.

When -z output option is in effect, the output is formatted this way:

12README NUL31NUL arch/i386/Makefile NUL arch/x86/Makefile NUL

That is:

  1. the number of added lines;

  2. a tab;

  3. the number of deleted lines;

  4. a tab;

  5. a NUL (only exists if renamed/copied);

  6. pathname in preimage;

  7. a NUL (only exists if renamed/copied);

  8. pathname in postimage (only exists if renamed/copied);

  9. a NUL.

The extra NUL before the preimage path in renamed case is to allowscripts that read the output to tell if the current record being read isa single-path record or a rename/copy record without reading ahead.After reading added and deleted lines, reading up to NUL would yieldthe pathname, but if that is NUL, the record will show two paths.

Top Articles
Latest Posts
Article information

Author: Zonia Mosciski DO

Last Updated: 04/10/2023

Views: 6058

Rating: 4 / 5 (71 voted)

Reviews: 86% of readers found this page helpful

Author information

Name: Zonia Mosciski DO

Birthday: 1996-05-16

Address: Suite 228 919 Deana Ford, Lake Meridithberg, NE 60017-4257

Phone: +2613987384138

Job: Chief Retail Officer

Hobby: Tai chi, Dowsing, Poi, Letterboxing, Watching movies, Video gaming, Singing

Introduction: My name is Zonia Mosciski DO, I am a enchanting, joyous, lovely, successful, hilarious, tender, outstanding person who loves writing and wants to share my knowledge and understanding with you.