merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

1 files changed, 197 insertions, 0 deletions

diff --git a/third_party/git/Documentation/diff-generate-patch.txt b/third_party/git/Documentation/diff-generate-patch.txt
new file mode 100644
index 0000000000..f10ca410ad
--- /dev/null
+++ b/third_party/git/Documentation/diff-generate-patch.txt
@@ -0,0 +1,197 @@
+Generating patches with -p
+--------------------------
+
+When "git-diff-index", "git-diff-tree", or "git-diff-files" are run
+with a `-p` option, "git diff" without the `--raw` option, or
+"git log" with the "-p" option, they
+do not produce the output described above; 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.
+
+What the -p option produces is slightly different from the traditional
+diff 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 is
+involved.  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 the
+name of the source file of the rename/copy and the name of
+the 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 type
+and 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, and
+the dissimilarity index is the percentage of changed lines.  It
+is a rounded down integer, followed by a percent sign.  The
+similarity index value of 100% is thus reserved for two equal
+files, while 100% dissimilarity means that no line from the old
+file made it into the new one.
++
+The index line includes the SHA-1 checksum 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 for
+    the configuration variable `core.quotePath` (see
+    linkgit:git-config[1]).
+
+4.  All the `file1` files in the output refer to files before the
+    commit, and all the `file2` files refer to files after the commit.
+    It is incorrect to apply each change to each file sequentially.  For
+    example, this patch will swap a and b:
+
+      diff --git a/a b/b
+      rename from a
+      rename to b
+      diff --git a/b b/a
+      rename from b
+      rename to a
+
+
+combined diff format
+--------------------
+
+Any diff-generating command can take the `-c` or `--cc` option to
+produce a 'combined diff' when showing a merge. This is the default
+format when showing merges with linkgit:git-diff[1] or
+linkgit:git-show[1]. Note also that you can give the `-m` option to any
+of these commands to force generation of diffs with individual parents
+of a merge.
+
+A 'combined diff' format 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 --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 of
+the <mode> is different 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.
++
+However, if the --combined-all-paths option is provided, instead of a
+two-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 is
+active, to allow you to see the original name of the file in different
+parents.
+
+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 result,
+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 or file2).  Also eight 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").