Merge branch 'jc/am-3-fallback-regression-fix' into maint

"git am -3" had a small regression where it is aborted in its error
handling codepath when underlying merge-recursive failed in certain
ways, as it assumed that the internal call to merge-recursive will
never die, which is not the case (yet).

* jc/am-3-fallback-regression-fix:
am -3: do not let failed merge from completing the error codepath

diff --combined builtin/am.c
index 98e29e044eabc8d8ff43bcc6fb09eb19dacd66d2,c869796ea6e8faab62b4c258a2a84ad3254d520f..4e396c832139aa3c4ae4e68e9d265b0107817aa9
--- 1/builtin/am.c
--- 2/builtin/am.c
+++ b/builtin/am.c
@@@ -1343,7 -1343,7 +1343,7 @@@ static int parse_mail(struct am_state *
        strbuf_addstr(&msg, "\n\n");
        if (strbuf_read_file(&msg, am_path(state, "msg"), 0) < 0)
                die_errno(_("could not read '%s'"), am_path(state, "msg"));
 -      stripspace(&msg, 0);
 +      strbuf_stripspace(&msg, 0);
  
        if (state->signoff)
                am_signoff(&msg);
@@@ -1589,6 -1589,38 +1589,38 @@@ static int build_fake_ancestor(const st
        return 0;
  }
  
+ /**
+  * Do the three-way merge using fake ancestor, his tree constructed
+  * from the fake ancestor and the postimage of the patch, and our
+  * state.
+  */
+ static int run_fallback_merge_recursive(const struct am_state *state,
+                                       unsigned char *orig_tree,
+                                       unsigned char *our_tree,
+                                       unsigned char *his_tree)
+ {
+       struct child_process cp = CHILD_PROCESS_INIT;
+       int status;
+ 
+       cp.git_cmd = 1;
+ 
+       argv_array_pushf(&cp.env_array, "GITHEAD_%s=%.*s",
+                        sha1_to_hex(his_tree), linelen(state->msg), state->msg);
+       if (state->quiet)
+               argv_array_push(&cp.env_array, "GIT_MERGE_VERBOSITY=0");
+ 
+       argv_array_push(&cp.args, "merge-recursive");
+       argv_array_push(&cp.args, sha1_to_hex(orig_tree));
+       argv_array_push(&cp.args, "--");
+       argv_array_push(&cp.args, sha1_to_hex(our_tree));
+       argv_array_push(&cp.args, sha1_to_hex(his_tree));
+ 
+       status = run_command(&cp) ? (-1) : 0;
+       discard_cache();
+       read_cache();
+       return status;
+ }
+ 
  /**
   * Attempt a threeway merge, using index_path as the temporary index.
   */
@@@ -1596,10 -1628,6 +1628,6 @@@ static int fall_back_threeway(const str
  {
        unsigned char orig_tree[GIT_SHA1_RAWSZ], his_tree[GIT_SHA1_RAWSZ],
                      our_tree[GIT_SHA1_RAWSZ];
-       const unsigned char *bases[1] = {orig_tree};
-       struct merge_options o;
-       struct commit *result;
-       char *his_tree_name;
  
        if (get_sha1("HEAD", our_tree) < 0)
                hashcpy(our_tree, EMPTY_TREE_SHA1_BIN);
@@@ -1651,22 -1679,11 +1679,11 @@@
         * changes.
         */
  
-       init_merge_options(&o);
- 
-       o.branch1 = "HEAD";
-       his_tree_name = xstrfmt("%.*s", linelen(state->msg), state->msg);
-       o.branch2 = his_tree_name;
- 
-       if (state->quiet)
-               o.verbosity = 0;
- 
-       if (merge_recursive_generic(&o, our_tree, his_tree, 1, bases, &result)) {
+       if (run_fallback_merge_recursive(state, orig_tree, our_tree, his_tree)) {
                rerere(state->allow_rerere_autoupdate);
-               free(his_tree_name);
                return error(_("Failed to merge in the changes."));
        }
  
-       free(his_tree_name);
        return 0;
  }
  
@@@ -2208,17 -2225,6 +2225,17 @@@ enum resume_mode 
        RESUME_ABORT
  };
  
 +static int git_am_config(const char *k, const char *v, void *cb)
 +{
 +      int status;
 +
 +      status = git_gpg_config(k, v, NULL);
 +      if (status)
 +              return status;
 +
 +      return git_default_config(k, v, NULL);
 +}
 +
  int cmd_am(int argc, const char **argv, const char *prefix)
  {
        struct am_state state;
@@@ -2229,8 -2235,8 +2246,8 @@@
        int in_progress;
  
        const char * const usage[] = {
 -              N_("git am [options] [(<mbox>|<Maildir>)...]"),
 -              N_("git am [options] (--continue | --skip | --abort)"),
 +              N_("git am [<options>] [(<mbox>|<Maildir>)...]"),
 +              N_("git am [<options>] (--continue | --skip | --abort)"),
                NULL
        };
  
@@@ -2319,7 -2325,7 +2336,7 @@@
                OPT_END()
        };
  
 -      git_config(git_default_config, NULL);
 +      git_config(git_am_config, NULL);
  
        am_state_init(&state, git_path("rebase-apply"));