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