rebase -i: Inline expression

Inline expression when generating output rather than overwriting the
"sha1" local variable with a short SHA1.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase--interactive.sh

@@ -167,8 +167,7 @@ pick_one () {
 	if test -z "$no_ff" -a "$current_sha1" = "$parent_sha1"
 	then
 		output git reset --hard $sha1
-		sha1=$(git rev-parse --short $sha1)
-		output warn Fast-forward to $sha1
+		output warn Fast-forward to $(git rev-parse --short $sha1)
 	else
 		output git cherry-pick "$@"
 	fi