Merge branch 'pb/merge-autostash-more' into jch

The local changes stashed by "git merge --autostash" were lost when
the merge failed in certain ways, which has been corrected.

* pb/merge-autostash-more:
  merge: apply autostash if merge strategy fails
  merge: apply autostash if fast-forward fails
  Documentation: define 'MERGE_AUTOSTASH'
  merge: add missing word "strategy" to a message

Documentation/merge-options.txt

@@ -154,7 +154,8 @@ endif::git-pull[]
 --autostash::
 --no-autostash::
 	Automatically create a temporary stash entry before the operation
-	begins, and apply it after the operation ends.  This means
+	begins, record it in the special ref `MERGE_AUTOSTASH`
+	and apply it after the operation ends.  This means
 	that you can run the operation on a dirty worktree.  However, use
 	with care: the final stash application after a successful
 	merge might result in non-trivial conflicts.

builtin/merge.c

@@ -1561,6 +1561,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 					  &head_commit->object.oid,
 					  &commit->object.oid,
 					  overwrite_ignore)) {
+			apply_autostash(git_path_merge_autostash(the_repository));
 			ret = 1;
 			goto done;
 		}
@@ -1709,14 +1710,15 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		else
 			fprintf(stderr, _("Merge with strategy %s failed.\n"),
 				use_strategies[0]->name);
+		apply_autostash(git_path_merge_autostash(the_repository));
 		ret = 2;
 		goto done;
 	} else if (best_strategy == wt_strategy)
 		; /* We already have its result in the working tree. */
 	else {
 		printf(_("Rewinding the tree to pristine...\n"));
 		restore_state(&head_commit->object.oid, &stash);
-		printf(_("Using the %s to prepare resolving by hand.\n"),
+		printf(_("Using the %s strategy to prepare resolving by hand.\n"),
 			best_strategy);
 		try_merge_strategy(best_strategy, common, remoteheads,
 				   head_commit);

t/t7600-merge.sh

@@ -122,6 +122,8 @@ test_expect_success 'setup' '
 	c0=$(git rev-parse HEAD) &&
 	cp file.1 file &&
 	git add file &&
+	cp file.1 other &&
+	git add other &&
 	test_tick &&
 	git commit -m "commit 1" &&
 	git tag c1 &&
@@ -711,6 +713,15 @@ test_expect_success 'fast-forward merge with --autostash' '
 	test_cmp result.1-5 file
 '
 
+test_expect_success 'failed fast-forward merge with --autostash' '
+	git reset --hard c0 &&
+	git merge-file file file.orig file.5 &&
+	cp file.5 other &&
+	test_must_fail git merge --autostash c1 2>err &&
+	test_i18ngrep "Applied autostash." err &&
+	test_cmp file.5 file
+'
+
 test_expect_success 'octopus merge with --autostash' '
 	git reset --hard c1 &&
 	git merge-file file file.orig file.3 &&
@@ -721,6 +732,14 @@ test_expect_success 'octopus merge with --autostash' '
 	test_cmp result.1-3-5-9 file
 '
 
+test_expect_success 'failed merge (exit 2) with --autostash' '
+	git reset --hard c1 &&
+	git merge-file file file.orig file.5 &&
+	test_must_fail git merge -s recursive --autostash c2 c3 2>err &&
+	test_i18ngrep "Applied autostash." err &&
+	test_cmp result.1-5 file
+'
+
 test_expect_success 'conflicted merge with --autostash, --abort restores stash' '
 	git reset --hard c3 &&
 	cp file.1 file &&