Merge branch 'so/cherry-pick-always-allow-m1'

"git cherry-pick -m1" was forbidden when picking a non-merge
commit, even though there _is_ parent number 1 for such a commit.
This was done to avoid mistakes back when "cherry-pick" was about
picking a single commit, but is no longer useful with "cherry-pick"
that can pick a range of commits.  Now the "-m$num" option is
allowed when picking any commit, as long as $num names an existing
parent of the commit.

Technically this is a backward incompatible change; hopefully
nobody is relying on the error-checking behaviour.

* so/cherry-pick-always-allow-m1:
  t3506: validate '-m 1 -ff' is now accepted for non-merge commits
  t3502: validate '-m 1' argument is now accepted for non-merge commits
  cherry-pick: do not error on non-merge commits when '-m 1' is specified
  t3510: stop using '-m 1' to force failure mid-sequence of cherry-picks

1 files changed, 7 insertions, 3 deletions

diff --git a/sequencer.c b/sequencer.c
index 4f1cb5e38f..f5370f4965 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1790,9 +1790,13 @@ static int do_pick_commit(struct repository *r,
 			return error(_("commit %s does not have parent %d"),
 				oid_to_hex(&commit->object.oid), opts->mainline);
 		parent = p->item;
-	} else if (0 < opts->mainline)
-		return error(_("mainline was specified but commit %s is not a merge."),
-			oid_to_hex(&commit->object.oid));
+	} else if (1 < opts->mainline)
+		/*
+		 *  Non-first parent explicitly specified as mainline for
+		 *  non-merge commit
+		 */
+		return error(_("commit %s does not have parent %d"),
+			     oid_to_hex(&commit->object.oid), opts->mainline);
 	else
 		parent = commit->parents->item;