Merge branch 'ct/diff-with-merge-base-clarification' into master

Doc update.

* ct/diff-with-merge-base-clarification:
  git-diff.txt: reorder possible usages
  git-diff.txt: don't mark required argument as optional

Author: gitster

Documentation/git-diff.txt

@@ -63,13 +63,7 @@ files on disk.
 	This is to view the changes between two arbitrary
 	<commit>.
 
-'git diff' [<options>] <commit>..<commit> [--] [<path>...]::
-
-	This is synonymous to the previous form.  If <commit> on
-	one side is omitted, it will have the same effect as
-	using HEAD instead.
-
-'git diff' [<options>] <commit> [<commit>...] <commit> [--] [<path>...]::
+'git diff' [<options>] <commit> <commit>... <commit> [--] [<path>...]::
 
 	This form is to view the results of a merge commit.  The first
 	listed <commit> must be the merge itself; the remaining two or
@@ -78,6 +72,13 @@ files on disk.
 	For instance, if `master` names a merge commit, `git diff master
 	master^@` gives the same combined diff as `git show master`.
 
+'git diff' [<options>] <commit>..<commit> [--] [<path>...]::
+
+	This is synonymous to the earlier form (without the "..") for
+	viewing the changes between two arbitrary <commit>.  If <commit> on
+	one side is omitted, it will have the same effect as
+	using HEAD instead.
+
 'git diff' [<options>] <commit>\...<commit> [--] [<path>...]::
 
 	This form is to view the changes on the branch containing