[RFC/PATCH v1] merge - make squash a 1-step operation

[Edmundo Carmona Antoranz <eantoranz@gmail.com>]

---
 builtin/merge.c | 63 +++++++++++++++++++++++++------------------------
 1 file changed, 32 insertions(+), 31 deletions(-)

diff --git a/builtin/merge.c b/builtin/merge.c
index 6e99aead46..d5745a7888 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -64,6 +64,7 @@ static int option_edit = -1;
 static int allow_trivial = 1, have_message, verify_signatures;
 static int overwrite_ignore = 1;
 static struct strbuf merge_msg = STRBUF_INIT;
+static struct strbuf squash_msg = STRBUF_INIT;
 static struct strategy **use_strategies;
 static size_t use_strategies_nr, use_strategies_alloc;
 static const char **xopts;
@@ -390,12 +391,9 @@ static void finish_up_to_date(const char *msg)
 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 {
 	struct rev_info rev;
-	struct strbuf out = STRBUF_INIT;
 	struct commit_list *j;
 	struct pretty_print_context ctx = {0};
 
-	printf(_("Squash commit -- not updating HEAD\n"));
-
 	repo_init_revisions(the_repository, &rev, NULL);
 	rev.ignore_merges = 1;
 	rev.commit_format = CMIT_FMT_MEDIUM;
@@ -414,15 +412,13 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
 	ctx.date_mode = rev.date_mode;
 	ctx.fmt = rev.commit_format;
 
-	strbuf_addstr(&out, "Squashed commit of the following:\n");
+	strbuf_addstr(&squash_msg, "Squashed commit of the following:\n");
 	while ((commit = get_revision(&rev)) != NULL) {
-		strbuf_addch(&out, '\n');
-		strbuf_addf(&out, "commit %s\n",
+		strbuf_addch(&squash_msg, '\n');
+		strbuf_addf(&squash_msg, "commit %s\n",
 			oid_to_hex(&commit->object.oid));
-		pretty_print_commit(&ctx, commit, &out);
+		pretty_print_commit(&ctx, commit, &squash_msg);
 	}
-	write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
-	strbuf_release(&out);
 }
 
 static void finish(struct commit *head_commit,
@@ -440,8 +436,12 @@ static void finish(struct commit *head_commit,
 		strbuf_addf(&reflog_message, "%s: %s",
 			getenv("GIT_REFLOG_ACTION"), msg);
 	}
-	if (squash) {
+	if (squash && !squash_msg.len) {
+		// message hasn't been calculated, that means we are stopping the squash process so the user can finish it
 		squash_message(head_commit, remoteheads);
+		write_file_buf(git_path_squash_msg(the_repository), squash_msg.buf, squash_msg.len);
+		if (option_commit > 0)
+			printf(_("Squash conflicts -- not updating HEAD\n"));
 	} else {
 		if (verbosity >= 0 && !merge_msg.len)
 			printf(_("No merge message -- not updating HEAD\n"));
@@ -893,13 +893,21 @@ static int finish_automerge(struct commit *head,
 	struct object_id result_commit;
 
 	free_commit_list(common);
-	parents = remoteheads;
-	if (!head_subsumed || fast_forward == FF_NO)
-		commit_list_insert(head, &parents);
-	prepare_to_commit(remoteheads);
-	if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
-			&result_commit, NULL, sign_commit))
-		die(_("failed to write commit object"));
+	if (squash) {
+		squash_message(head, remoteheads);
+		parents = commit_list_insert(head, &parents);
+		if (commit_tree(squash_msg.buf, squash_msg.len, result_tree, parents,
+				&result_commit, NULL, sign_commit))
+			die(_("failed to write commit object on squash"));
+	} else {
+		parents = remoteheads;
+		if (!head_subsumed || fast_forward == FF_NO)
+			commit_list_insert(head, &parents);
+		prepare_to_commit(remoteheads);
+		if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
+				&result_commit, NULL, sign_commit))
+			die(_("failed to write commit object"));
+	}
 	strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 	finish(head, remoteheads, &result_commit, buf.buf);
 	strbuf_release(&buf);
@@ -1342,18 +1350,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	if (verbosity < 0)
 		show_diffstat = 0;
 
-	if (squash) {
-		if (fast_forward == FF_NO)
-			die(_("You cannot combine --squash with --no-ff."));
-		if (option_commit > 0)
-			die(_("You cannot combine --squash with --commit."));
-		/*
-		 * squash can now silently disable option_commit - this is not
-		 * a problem as it is only overriding the default, not a user
-		 * supplied option.
-		 */
-		option_commit = 0;
-	}
+	if (squash && fast_forward == FF_NO)
+		die(_("You cannot combine --squash with --no-ff."));
 
 	if (option_commit < 0)
 		option_commit = 1;
@@ -1682,8 +1680,11 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		write_merge_state(remoteheads);
 
 	if (merge_was_ok)
-		fprintf(stderr, _("Automatic merge went well; "
-			"stopped before committing as requested\n"));
+		if (!option_commit)
+			fprintf(stderr, _("Automatic merge went well; "
+				"stopped before committing as requested\n"));
+		else
+			;
 	else
 		ret = suggest_conflicts();
 
-- 
2.22.0.214.g8dca754b1e.dirty