[PATCH] cherry-pick: better error message when the parameter is a non-commit

[Miklos Vajna <vmiklos@suse.cz>]

When copy&paste goes wrong, and the user e.g. tries to cherry-pick a
blob, the error message used to be:

	fatal: BUG: expected exactly one commit from walk

Instead, now it is:

	fatal: Can't cherry-pick a blob

Signed-off-by: Miklos Vajna <vmiklos@suse.cz>
---
 sequencer.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/sequencer.c b/sequencer.c
index baa0310..0ac00d4 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1082,8 +1082,15 @@ int sequencer_pick_revisions(struct replay_opts *opts)
 		if (prepare_revision_walk(opts->revs))
 			die(_("revision walk setup failed"));
 		cmit = get_revision(opts->revs);
-		if (!cmit || get_revision(opts->revs))
+		if (!cmit || get_revision(opts->revs)) {
+			unsigned char sha1[20];
+			if (!get_sha1(opts->revs->cmdline.rev->name, sha1)) {
+				enum object_type type = sha1_object_info(sha1, NULL);
+				if (type > 0 && type != OBJ_COMMIT)
+					die(_("Can't cherry-pick a %s"), typename(type));
+			}
 			die("BUG: expected exactly one commit from walk");
+		}
 		return single_pick(cmit, opts);
 	}
 
-- 
1.8.1.4