From 1f010d6bdf756129db13d1367c888aa4153f6d87 Mon Sep 17 00:00:00 2001
From: "brian m. carlson" <sandals@crustytoothpaste.net>
Date: Mon, 20 Jan 2025 01:56:02 +0000
Subject: doc: use .adoc extension for AsciiDoc files

We presently use the ".txt" extension for our AsciiDoc files.  While not
wrong, most editors do not associate this extension with AsciiDoc,
meaning that contributors don't get automatic editor functionality that
could be useful, such as syntax highlighting and prose linting.

It is much more common to use the ".adoc" extension for AsciiDoc files,
since this helps editors automatically detect files and also allows
various forges to provide rich (HTML-like) rendering.  Let's do that
here, renaming all of the files and updating the includes where
relevant.  Adjust the various build scripts and makefiles to use the new
extension as well.

Note that this should not result in any user-visible changes to the
documentation.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/diff-generate-patch.adoc | 210 +++++++++++++++++++++++++++++++++
 1 file changed, 210 insertions(+)
 create mode 100644 Documentation/diff-generate-patch.adoc

(limited to 'Documentation/diff-generate-patch.adoc')

diff --git a/Documentation/diff-generate-patch.adoc b/Documentation/diff-generate-patch.adoc
new file mode 100644
index 0000000000..e5c813c96f
--- /dev/null
+++ b/Documentation/diff-generate-patch.adoc
@@ -0,0 +1,210 @@
+[[generate_patch_text_with_p]]
+Generating patch text with -p
+-----------------------------
+
+Running
+linkgit:git-diff[1],
+linkgit:git-log[1],
+linkgit:git-show[1],
+linkgit:git-diff-index[1],
+linkgit:git-diff-tree[1], or
+linkgit:git-diff-files[1]
+with the `-p` option produces patch text.
+You can customize the creation of patch text via the
+`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables
+(see linkgit:git[1]), and the `diff` attribute (see linkgit:gitattributes[5]).
+
+What the `-p` option produces is slightly different from the traditional
+diff format:
+
+1.   It is preceded by 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 a 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 the rename/copy produces, respectively.
+
+2.   It is followed by one or more extended header lines:
++
+[synopsis]
+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 _<mode>_ 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 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 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
+
+5.  Hunk headers mention the name of the function to which the hunk
+    applies.  See "Defining a custom hunk-header" in
+    linkgit:gitattributes[5] for details of how to tailor this to
+    specific languages.
+
+
+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 suitable
+`--diff-merges` option to any of these commands to force generation of
+diffs in a specific format.
+
+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 by a "git diff" header, that looks like
+     this (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):
++
+[synopsis]
+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 content movement (renames and
+copying detection) are designed to work with the diff of two
+_<tree-ish>_ and are not used by combined diff format.
+
+3.   It is followed by a two-line from-file/to-file header:
+
+       --- a/file
+       +++ b/file
++
+Similar to the two-line header for the 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 an 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 to be applied. 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").
-- 
cgit v1.3

