cherry-pick: handle root commits with external strategies

diff --git a/builtin/merge.c b/builtin/merge.c
index d54e7ddbb12286beb4f9622864f2eeaa79453d32..8a0f6901f90c9728fb7521121ead030325ce3a45 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -590,6 +590,14 @@ static void write_tree_trivial(unsigned char *sha1)
                die(_("git write-tree failed to write a tree"));
 }
 
+static const char *merge_argument(struct commit *commit)
+{
+       if (commit)
+               return sha1_to_hex(commit->object.sha1);
+       else
+               return EMPTY_TREE_SHA1_HEX;
+}
+
 int try_merge_command(const char *strategy, size_t xopts_nr,
                      const char **xopts, struct commit_list *common,
                      const char *head_arg, struct commit_list *remotes)
@@ -610,11 +618,11 @@ int try_merge_command(const char *strategy, size_t xopts_nr,
                args[i++] = s;
        }
        for (j = common; j; j = j->next)
-               args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
+               args[i++] = xstrdup(merge_argument(j->item));
        args[i++] = "--";
        args[i++] = head_arg;
        for (j = remotes; j; j = j->next)
-               args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
+               args[i++] = xstrdup(merge_argument(j->item));
        args[i] = NULL;
        ret = run_command_v_opt(args, RUN_GIT_CMD);
        strbuf_release(&buf);