doc/git-log: move "Diff Formatting" from rev-list-options

Our rev-list-options.txt include has a "Diff Formatting" section, but it
is ifndef'd out for all manpages except git-log. And a few bits of the
text are rather out of date.

We say "some of these options are specific to git-rev-list". That's
obviously silly since we (even before this patch) show the content only
for git-log. But moreover, it's not true; each of the listed options is
meaningful for other diff commands.

We also say "...however other diff options may be given. See git-diff-files
for more options." But there's no need to do so; git-log already has a
"Common Diff Options" section which includes diff-options.txt.

So let's move these options over to git-log and put them with the other
diff options, giving a single "diff" section for the git-log
documentation. We'll call it "Diff Formatting" but use the all-caps
top-level header to match its sibling sections. And we'll rewrite the
section intro to remove the useless bits and give a more generic
overview of the section which can be later extended.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -111,8 +111,46 @@ include::rev-list-options.txt[]
 
 include::pretty-formats.txt[]
 
-COMMON DIFF OPTIONS
--------------------
+DIFF FORMATTING
+---------------
+
+By default, `git log` does not generate any diff output. The options
+below can be used to show the changes made by each commit.
+
+-c::
+	With this option, diff output for a merge commit
+	shows the differences from each of the parents to the merge result
+	simultaneously instead of showing pairwise diff between a parent
+	and the result one at a time. Furthermore, it lists only files
+	which were modified from all parents.
+
+--cc::
+	This flag implies the `-c` option and further compresses the
+	patch output by omitting uninteresting hunks whose contents in
+	the parents have only two variants and the merge result picks
+	one of them without modification.
+
+--combined-all-paths::
+	This flag causes combined diffs (used for merge commits) to
+	list the name of the file from all parents.  It thus only has
+	effect when -c or --cc are specified, and is likely only
+	useful if filename changes are detected (i.e. when either
+	rename or copy detection have been requested).
+
+-m::
+--diff-merges::
+	This flag makes the merge commits show the full diff like
+	regular commits; for each merge parent, a separate log entry
+	and diff is generated. An exception is that only diff against
+	the first parent is shown when `--first-parent` option is given;
+	in that case, the output represents the changes the merge
+	brought _into_ the then-current branch.
+
+-r::
+	Show recursive diffs.
+
+-t::
+	Show the tree objects in the diff output. This implies `-r`.
 
 :git-log: 1
 include::diff-options.txt[]

Documentation/rev-list-options.txt

@@ -1117,49 +1117,3 @@ ifdef::git-rev-list[]
 	by a tab.
 endif::git-rev-list[]
 endif::git-shortlog[]
-
-ifndef::git-shortlog[]
-ifndef::git-rev-list[]
-Diff Formatting
-~~~~~~~~~~~~~~~
-
-Listed below are options that control the formatting of diff output.
-Some of them are specific to linkgit:git-rev-list[1], however other diff
-options may be given. See linkgit:git-diff-files[1] for more options.
-
--c::
-	With this option, diff output for a merge commit
-	shows the differences from each of the parents to the merge result
-	simultaneously instead of showing pairwise diff between a parent
-	and the result one at a time. Furthermore, it lists only files
-	which were modified from all parents.
-
---cc::
-	This flag implies the `-c` option and further compresses the
-	patch output by omitting uninteresting hunks whose contents in
-	the parents have only two variants and the merge result picks
-	one of them without modification.
-
---combined-all-paths::
-	This flag causes combined diffs (used for merge commits) to
-	list the name of the file from all parents.  It thus only has
-	effect when -c or --cc are specified, and is likely only
-	useful if filename changes are detected (i.e. when either
-	rename or copy detection have been requested).
-
--m::
---diff-merges::
-	This flag makes the merge commits show the full diff like
-	regular commits; for each merge parent, a separate log entry
-	and diff is generated. An exception is that only diff against
-	the first parent is shown when `--first-parent` option is given;
-	in that case, the output represents the changes the merge
-	brought _into_ the then-current branch.
-
--r::
-	Show recursive diffs.
-
--t::
-	Show the tree objects in the diff output. This implies `-r`.
-endif::git-rev-list[]
-endif::git-shortlog[]