Documentation/git-log: Clarify --full-diff

The current description gives the impression that "--full-diff" affects
"log -p" only.

Make it clearer that it affects all diff-based output types.
Signed-off-by: NMichael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -55,6 +55,9 @@ OPTIONS
 	paths.  With this, the full diff is shown for commits that touch
 	the specified paths; this means that "<path>..." limits only
 	commits, and doesn't limit diff for those commits.
++
+Note that this affects all diff-based output types, e.g. those
+produced by --stat etc.
 
 --log-size::
 	Before the log message print out its size in bytes. Intended