whatchanged: document -m option from git-diff-tree.

The documentation for git-whatchanged is meant to describe only
the most frequently used options from git-diff-tree.  Because "why
doesn't it show merges" was asked more than once, we'd better
describe '-m' option there.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/Documentation/git-whatchanged.txt b/Documentation/git-whatchanged.txt
index 056a969..db2efea 100644 (file)
--- a/Documentation/git-whatchanged.txt
+++ b/Documentation/git-whatchanged.txt
@@ -44,6 +44,13 @@ OPTIONS
        <format> can be one of 'raw', 'medium', 'short', 'full',
        and 'oneline'.
 
+-m::
+       By default, differences for merge commits are not shown.
+       With this flag, show differences to that commit from all
+       of its parents.
+
+       However, it is not very useful in general, although it
+       *is* useful on a file-by-file basis.
 
 Author
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