revert: improve success message by adding abbreviated commit sha1

Instead of saying "Finished one cherry-pick." or "Finished one revert.",
we now say "Finished cherry-pick of commit <abbreviated sha1>." or
"Finished revert of commit <abbreviated sha1>." which is more informative,
especially when cherry-picking or reverting many commits.

In case of failure the message is now "Automatic cherry-pick of commit
<abbreviated sha1> failed." instead of "Automatic cherry-pick failed."

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/revert.c

@@ -492,7 +492,8 @@ static int do_pick_commit(void)
 		}
 	}
 
-	strbuf_addstr(&mebuf, me);
+	strbuf_addf(&mebuf, "%s of commit %s", me,
+		    find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 
 	if (!strategy || !strcmp(strategy, "recursive") || action == REVERT) {
 		res = do_recursive_merge(base, next, base_label, next_label,
@@ -521,7 +522,7 @@ static int do_pick_commit(void)
 		if (!no_commit)
 			res = run_git_commit(defmsg);
 		if (!res)
-			fprintf(stderr, "Finished one %s.\n", mebuf.buf);
+			fprintf(stderr, "Finished %s.\n", mebuf.buf);
 	}
 
 	strbuf_release(&mebuf);

t/t3508-cherry-pick-many-commits.sh

@@ -23,10 +23,10 @@ test_expect_success setup '
 '
 
 test_expect_success 'cherry-pick first..fourth works' '
-	cat <<-\EOF >expected &&
-	Finished one cherry-pick.
-	Finished one cherry-pick.
-	Finished one cherry-pick.
+	cat <<-EOF >expected &&
+	Finished cherry-pick of commit $(git rev-parse --short second).
+	Finished cherry-pick of commit $(git rev-parse --short third).
+	Finished cherry-pick of commit $(git rev-parse --short fourth).
 	EOF
 
 	git checkout -f master &&
@@ -40,10 +40,10 @@ test_expect_success 'cherry-pick first..fourth works' '
 '
 
 test_expect_success 'cherry-pick --strategy resolve first..fourth works' '
-	cat <<-\EOF >expected &&
-	Finished one cherry-pick with strategy resolve.
-	Finished one cherry-pick with strategy resolve.
-	Finished one cherry-pick with strategy resolve.
+	cat <<-EOF >expected &&
+	Finished cherry-pick of commit $(git rev-parse --short second) with strategy resolve.
+	Finished cherry-pick of commit $(git rev-parse --short third) with strategy resolve.
+	Finished cherry-pick of commit $(git rev-parse --short fourth) with strategy resolve.
 	EOF
 
 	git checkout -f master &&