Merge branch 'mg/cherry-pick-multi-on-unborn' into maint

"git cherry-pick A" worked on an unborn branch, but "git
cherry-pick A..B" didn't.

* mg/cherry-pick-multi-on-unborn:
  cherry-pick: allow to pick to unborn branches

diff --cc sequencer.c
index 4687ad4b80bf651fd9dab66916681b71f7a6e31d,c051d134c2398b3d227ae42e1d54d77846ebb904..c6362d63f35fe37d67fa235784ab8ce75a60db44
--- 1/sequencer.c
--- 2/sequencer.c
+++ b/sequencer.c
@@@ -885,9 -916,13 +885,13 @@@ static int sequencer_rollback(struct re
        fclose(f);
        if (get_sha1_hex(buf.buf, sha1) || buf.buf[40] != '\0') {
                error(_("stored pre-cherry-pick HEAD file '%s' is corrupt"),
 -                      filename);
 +                      git_path_head_file());
                goto fail;
        }
+       if (is_null_sha1(sha1)) {
+               error(_("cannot abort from a branch yet to be born"));
+               goto fail;
+       }
        if (reset_for_rollback(sha1))
                goto fail;
        remove_sequencer_state();