revert: allow reverting a root commit

Although it is probably an uncommon operation, there is no
reason to disallow it, as it works just fine. It is the
reverse of a cherry-pick of a root commit, which is already
allowed.

We do have to tweak one check on whether we have a merge
commit, which assumed we had at least one parent.

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

diff --git a/builtin/revert.c b/builtin/revert.c
index f697e6695374d06e7b08c9faac1ebaefe4ff31d7..1f27c63343904a969e60ab19408495007f59d133 100644 (file)
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -408,8 +408,6 @@ static int do_pick_commit(void)
        discard_cache();
 
        if (!commit->parents) {
-               if (action == REVERT)
-                       die (_("Cannot revert a root commit"));
                parent = NULL;
        }
        else if (commit->parents->next) {
@@ -467,7 +465,7 @@ static int do_pick_commit(void)
                strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
                strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 
-               if (commit->parents->next) {
+               if (commit->parents && commit->parents->next) {
                        strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
                        strbuf_addstr(&msgbuf, sha1_to_hex(parent->object.sha1));
                }