Reorganize `git-log' man page to clarify common diff options.

This will reduce considerably the common confusion where people miss the
`--follow' option, and wonder why `-M'/`-C' is not working.

* Move the diff options include to after the log-specific flags, and add
  a "Common diff options" subtitle before them.  (These options apply
  only when patches are shown, which is not a common use case among
  newbies, so having them first is confusing.)

* Move the `--follow' description to the top of the listed options.  The
  options before that seem less important: `--full-diff' applies only
  when patches are shown, `--source' and `--decorate' are less useful
  with many common commit specifications.

* Clarify that `--follow' works only for a single path argument.

Signed-off-by: Eli Barzilay <eli@barzilay.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -23,9 +23,6 @@ each commit introduces are shown.
 OPTIONS
 -------
 
-:git-log: 1
-include::diff-options.txt[]
-
 -<n>::
 	Limits the number of commits to show.
 
@@ -37,6 +34,10 @@ include::diff-options.txt[]
 	and <until>, see "SPECIFYING REVISIONS" section in
 	linkgit:git-rev-parse[1].
 
+--follow::
+	Continue listing the history of a file beyond renames
+	(works only for a single file).
+
 --no-decorate::
 --decorate[=short|full|no]::
 	Print out the ref names of any commits that are shown. If 'short' is
@@ -56,9 +57,6 @@ include::diff-options.txt[]
 	the specified paths; this means that "<path>..." limits only
 	commits, and doesn't limit diff for those commits.
 
---follow::
-	Continue listing the history of a file beyond renames/copies.
-
 --log-size::
 	Before the log message print out its size in bytes. Intended
 	mainly for porcelain tools consumption. If git is unable to
@@ -72,6 +70,11 @@ include::diff-options.txt[]
 	to be prefixed with "\-- " to separate them from options or
 	refnames.
 
+Common diff options
+~~~~~~~~~~~~~~~~~~~
+
+:git-log: 1
+include::diff-options.txt[]
 
 include::rev-list-options.txt[]