Merge branch 'nd/merge-quit'

"git merge" learned "--quit" option that cleans up the in-progress
merge while leaving the working tree and the index still in a mess.

* nd/merge-quit:
  merge: add --quit
  merge: remove drop_save() in favor of remove_merge_branch_state()

Documentation/git-merge.txt

@@ -100,6 +100,10 @@ commit or stash your changes before running 'git merge'.
 'git merge --abort' is equivalent to 'git reset --merge' when
 `MERGE_HEAD` is present.
 
+--quit::
+	Forget about the current merge in progress. Leave the index
+	and the working tree as-is.
+
 --continue::
 	After a 'git merge' stops due to conflicts you can conclude the
 	merge by running 'git merge --continue' (see "HOW TO RESOLVE

branch.c

@@ -338,14 +338,19 @@ void create_branch(struct repository *r,
 	free(real_ref);
 }
 
-void remove_branch_state(struct repository *r)
+void remove_merge_branch_state(struct repository *r)
 {
-	sequencer_post_commit_cleanup(r);
 	unlink(git_path_merge_head(r));
 	unlink(git_path_merge_rr(r));
 	unlink(git_path_merge_msg(r));
 	unlink(git_path_merge_mode(r));
+}
+
+void remove_branch_state(struct repository *r)
+{
+	sequencer_post_commit_cleanup(r);
 	unlink(git_path_squash_msg(r));
+	remove_merge_branch_state(r);
 }
 
 void die_if_checked_out(const char *branch, int ignore_current_worktree)

branch.h

@@ -60,6 +60,12 @@ int validate_branchname(const char *name, struct strbuf *ref);
  */
 int validate_new_branchname(const char *name, struct strbuf *ref, int force);
 
+/*
+ * Remove information about the merge state on the current
+ * branch. (E.g., MERGE_HEAD)
+ */
+void remove_merge_branch_state(struct repository *r);
+
 /*
  * Remove information about the state of working on the current
  * branch. (E.g., MERGE_HEAD)

builtin/merge.c

@@ -37,6 +37,7 @@
 #include "packfile.h"
 #include "tag.h"
 #include "alias.h"
+#include "branch.h"
 #include "commit-reach.h"
 #include "wt-status.h"
 
@@ -73,6 +74,7 @@ static int option_renormalize;
 static int verbosity;
 static int allow_rerere_auto;
 static int abort_current_merge;
+static int quit_current_merge;
 static int continue_current_merge;
 static int allow_unrelated_histories;
 static int show_progress = -1;
@@ -274,6 +276,8 @@ static struct option builtin_merge_options[] = {
 	OPT__VERBOSITY(&verbosity),
 	OPT_BOOL(0, "abort", &abort_current_merge,
 		N_("abort the current in-progress merge")),
+	OPT_BOOL(0, "quit", &quit_current_merge,
+		N_("--abort but leave index and working tree alone")),
 	OPT_BOOL(0, "continue", &continue_current_merge,
 		N_("continue the current in-progress merge")),
 	OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
@@ -287,14 +291,6 @@ static struct option builtin_merge_options[] = {
 	OPT_END()
 };
 
-/* Cleans up metadata that is uninteresting after a succeeded merge. */
-static void drop_save(void)
-{
-	unlink(git_path_merge_head(the_repository));
-	unlink(git_path_merge_msg(the_repository));
-	unlink(git_path_merge_mode(the_repository));
-}
-
 static int save_state(struct object_id *stash)
 {
 	int len;
@@ -388,7 +384,7 @@ static void finish_up_to_date(const char *msg)
 {
 	if (verbosity >= 0)
 		printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
-	drop_save();
+	remove_merge_branch_state(the_repository);
 }
 
 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
@@ -881,7 +877,7 @@ static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 			&result_commit, NULL, sign_commit))
 		die(_("failed to write commit object"));
 	finish(head, remoteheads, &result_commit, "In-index merge");
-	drop_save();
+	remove_merge_branch_state(the_repository);
 	return 0;
 }
 
@@ -907,7 +903,7 @@ static int finish_automerge(struct commit *head,
 	strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 	finish(head, remoteheads, &result_commit, buf.buf);
 	strbuf_release(&buf);
-	drop_save();
+	remove_merge_branch_state(the_repository);
 	return 0;
 }
 
@@ -1289,6 +1285,16 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		goto done;
 	}
 
+	if (quit_current_merge) {
+		if (orig_argc != 2)
+			usage_msg_opt(_("--quit expects no arguments"),
+				      builtin_merge_usage,
+				      builtin_merge_options);
+
+		remove_merge_branch_state(the_repository);
+		goto done;
+	}
+
 	if (continue_current_merge) {
 		int nargc = 1;
 		const char *nargv[] = {"commit", NULL};
@@ -1495,7 +1501,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		}
 
 		finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
-		drop_save();
+		remove_merge_branch_state(the_repository);
 		goto done;
 	} else if (!remoteheads->next && common->next)
 		;

t/t7600-merge.sh

@@ -867,4 +867,30 @@ test_expect_success EXECKEEPSPID 'killed merge can be completed with --continue'
 	verify_parents $c0 $c1
 '
 
+test_expect_success 'merge --quit' '
+	git init merge-quit &&
+	(
+		cd merge-quit &&
+		test_commit base &&
+		echo one >>base.t &&
+		git commit -am one &&
+		git branch one &&
+		git checkout base &&
+		echo two >>base.t &&
+		git commit -am two &&
+		test_must_fail git -c rerere.enabled=true merge one &&
+		test_path_is_file .git/MERGE_HEAD &&
+		test_path_is_file .git/MERGE_MODE &&
+		test_path_is_file .git/MERGE_MSG &&
+		git rerere status >rerere.before &&
+		git merge --quit &&
+		test_path_is_missing .git/MERGE_HEAD &&
+		test_path_is_missing .git/MERGE_MODE &&
+		test_path_is_missing .git/MERGE_MSG &&
+		git rerere status >rerere.after &&
+		test_must_be_empty rerere.after &&
+		! test_cmp rerere.after rerere.before
+	)
+'
+
 test_done