209 lines
7.1 KiB
Plaintext
209 lines
7.1 KiB
Plaintext
[[generate_patch_text_with_p]]
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Generating patch text with -p
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-----------------------------
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Running
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linkgit:git-diff[1],
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linkgit:git-log[1],
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linkgit:git-show[1],
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linkgit:git-diff-index[1],
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linkgit:git-diff-tree[1], or
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linkgit:git-diff-files[1]
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with the `-p` option produces patch text.
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You can customize the creation of patch text via the
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`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables
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(see linkgit:git[1]), and the `diff` attribute (see linkgit:gitattributes[5]).
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What the -p option produces is slightly different from the traditional
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diff format:
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1. It is preceded by a "git diff" header that looks like 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 the `a/` or `b/` filenames.
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+
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When a 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 the 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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+
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File modes are printed as 6-digit octal numbers including the file type
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and file permission bits.
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+
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Path names in extended headers do not include the `a/` and `b/` prefixes.
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+
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The similarity index is the percentage of unchanged lines, and
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the dissimilarity index is the percentage of changed lines. It
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is a rounded down integer, followed by a percent sign. The
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similarity index value of 100% is thus reserved for two equal
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files, while 100% dissimilarity means that no line from the old
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file made it into the new one.
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+
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The index line includes the blob object names before and after the change.
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The <mode> is included if the file mode does not change; otherwise,
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separate lines indicate the old and the new mode.
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3. Pathnames with "unusual" characters are quoted as explained for
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the configuration variable `core.quotePath` (see
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linkgit:git-config[1]).
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4. All the `file1` files in the output refer to files before the
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commit, and all the `file2` files refer to files after the commit.
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It is incorrect to apply each change to each file sequentially. For
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example, this patch will swap a and b:
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diff --git a/a b/b
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rename from a
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rename to b
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diff --git a/b b/a
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rename from b
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rename to a
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5. Hunk headers mention the name of the function to which the hunk
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applies. See "Defining a custom hunk-header" in
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linkgit:gitattributes[5] for details of how to tailor this to
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specific languages.
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Combined diff format
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--------------------
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Any diff-generating command can take the `-c` or `--cc` option to
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produce a 'combined diff' when showing a merge. This is the default
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format when showing merges with linkgit:git-diff[1] or
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linkgit:git-show[1]. Note also that you can give suitable
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`--diff-merges` option to any of these commands to force generation of
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diffs in a specific format.
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A "combined diff" format looks like this:
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------------
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diff --combined describe.c
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index fabadb8,cc95eb0..4866510
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--- a/describe.c
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+++ b/describe.c
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@@@ -98,20 -98,12 +98,20 @@@
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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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struct commit_list *list;
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static int initialized = 0;
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struct commit_name *n;
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+ if (get_sha1(arg, sha1) < 0)
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+ usage(describe_usage);
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+ cmit = lookup_commit_reference(sha1);
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+ if (!cmit)
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+ usage(describe_usage);
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+
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if (!initialized) {
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initialized = 1;
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for_each_ref(get_name);
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------------
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1. It is preceded by a "git diff" header, that looks like
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this (when the `-c` option is used):
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diff --combined file
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+
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or like this (when the `--cc` option is used):
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diff --cc file
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2. It is followed by one or more extended header lines
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(this example shows a merge with two parents):
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index <hash>,<hash>..<hash>
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mode <mode>,<mode>..<mode>
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new file mode <mode>
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deleted file mode <mode>,<mode>
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+
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The `mode <mode>,<mode>..<mode>` line appears only if at least one of
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the <mode> is different from the rest. Extended headers with
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information about detected content movement (renames and
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copying detection) are designed to work with the diff of two
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<tree-ish> and are not used by combined diff format.
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3. It is followed by a two-line from-file/to-file header:
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--- a/file
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+++ b/file
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+
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Similar to the two-line header for the traditional 'unified' diff
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format, `/dev/null` is used to signal created or deleted
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files.
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+
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However, if the --combined-all-paths option is provided, instead of a
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two-line from-file/to-file, you get an N+1 line from-file/to-file header,
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where N is the number of parents in the merge commit:
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--- a/file
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--- a/file
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--- a/file
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+++ b/file
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+
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This extended format can be useful if rename or copy detection is
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active, to allow you to see the original name of the file in different
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parents.
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4. Chunk header format is modified to prevent people from
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accidentally feeding it to `patch -p1`. Combined diff format
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was created for review of merge commit changes, and was not
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meant to be applied. The change is similar to the change in the
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extended 'index' header:
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@@@ <from-file-range> <from-file-range> <to-file-range> @@@
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+
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There are (number of parents + 1) `@` characters in the chunk
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header for combined diff format.
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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 result. A `+` character
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in the column N means that the line appears in the result,
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and fileN does not have that line (in other words, the line was
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added, from the point of view of that parent).
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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 or file2). Also, eight 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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