script with rev-list instead of log

Because log.decorate now shows decorations for --pretty=oneline,
we must explicitly turn it off when scripting. Otherwise,
users with log.decorate set will get cruft like:

  $ git stash
  Saved working directory and index state WIP on master:
    2c1f7f5 (HEAD, master) commit subject

Instead of adding --no-decorate to the log command line,
let's just use the rev-list plumbing interface instead,
which does the right thing.

git-submodule has a similar call. Since it just counts the
commit lines, nothing is broken, but let's switch it, too,
for the sake of consistency and cleanliness.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -643,7 +643,7 @@ cmd_summary() {
 				range=$sha1_dst
 			fi
 			GIT_DIR="$name/.git" \
-			git log --pretty=oneline --first-parent $range | wc -l
+			git rev-list --first-parent $range -- | wc -l
 			)
 			total_commits=" ($(($total_commits + 0)))"
 			;;