Fix grammatical error in git-revert

We always talk about "commit xyz".

We never talk about "xyz commit", except when we end up talking
about a commit as a branch head (notably, I would say "the HEAD
commit", or possibly "the top-of-master commit", but here
$commit is a SHA1 name, not anything else).

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-revert.sh

@@ -84,7 +84,7 @@ revert)
 		s/^[^ ]* /Revert "/
 		s/$/"/'
 	echo
-	echo "This reverts $commit commit."
+	echo "This reverts commit $commit."
 	test "$rev" = "$commit" ||
 	echo "(original 'git revert' arguments: $@)"
 	base=$commit next=$prev