merge-tree: add -X strategy option

Add merge strategy option to produce more customizable merge result such
as automatically resolving conflicts.

Signed-off-by: Tang Yuyi <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: WingT

builtin/merge-tree.c

@@ -18,6 +18,7 @@
 #include "quote.h"
 #include "tree.h"
 #include "config.h"
+#include "strvec.h"
 
 static int line_termination = '\n';
 
@@ -414,6 +415,7 @@ struct merge_tree_options {
 	int show_messages;
 	int name_only;
 	int use_stdin;
+	struct merge_options merge_options;
 };
 
 static int real_merge(struct merge_tree_options *o,
@@ -423,7 +425,7 @@ static int real_merge(struct merge_tree_options *o,
 {
 	struct commit *parent1, *parent2;
 	struct commit_list *merge_bases = NULL;
-	struct merge_options opt;
+	struct merge_options opt = o->merge_options;
 	struct merge_result result = { 0 };
 	int show_messages = o->show_messages;
 
@@ -437,8 +439,6 @@ static int real_merge(struct merge_tree_options *o,
 		help_unknown_ref(branch2, "merge-tree",
 				 _("not something we can merge"));
 
-	init_merge_options(&opt, the_repository);
-
 	opt.show_rename_progress = 0;
 
 	opt.branch1 = branch1;
@@ -513,6 +513,7 @@ static int real_merge(struct merge_tree_options *o,
 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 {
 	struct merge_tree_options o = { .show_messages = -1 };
+	struct strvec xopts = STRVEC_INIT;
 	int expected_remaining_argc;
 	int original_argc;
 	const char *merge_base = NULL;
@@ -548,14 +549,25 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 			   &merge_base,
 			   N_("commit"),
 			   N_("specify a merge-base for the merge")),
+		OPT_STRVEC('X', "strategy-option", &xopts, N_("option=value"),
+			N_("option for selected merge strategy")),
 		OPT_END()
 	};
 
+	/* Init merge options */
+	init_merge_options(&o.merge_options, the_repository);
+
 	/* Parse arguments */
 	original_argc = argc - 1; /* ignoring argv[0] */
 	argc = parse_options(argc, argv, prefix, mt_options,
 			     merge_tree_usage, PARSE_OPT_STOP_AT_NON_OPTION);
 
+	if (xopts.nr && o.mode == MODE_TRIVIAL)
+		die(_("--trivial-merge is incompatible with all other options"));
+	for (int x = 0; x < xopts.nr; x++)
+		if (parse_merge_opt(&o.merge_options, xopts.v[x]))
+			die(_("unknown strategy option: -X%s"), xopts.v[x]);
+
 	/* Handle --stdin */
 	if (o.use_stdin) {
 		struct strbuf buf = STRBUF_INIT;

t/t4301-merge-tree-write-tree.sh

@@ -22,6 +22,7 @@ test_expect_success setup '
 	git branch side1 &&
 	git branch side2 &&
 	git branch side3 &&
+	git branch side4 &&
 
 	git checkout side1 &&
 	test_write_lines 1 2 3 4 5 6 >numbers &&
@@ -46,6 +47,13 @@ test_expect_success setup '
 	test_tick &&
 	git commit -m rename-numbers &&
 
+	git checkout side4 &&
+	test_write_lines 0 1 2 3 4 5 >numbers &&
+	echo yo >greeting &&
+	git add numbers greeting &&
+	test_tick &&
+	git commit -m other-content-modifications &&
+
 	git switch --orphan unrelated &&
 	>something-else &&
 	git add something-else &&
@@ -97,6 +105,21 @@ test_expect_success 'Content merge and a few conflicts' '
 	test_cmp expect actual
 '
 
+test_expect_success 'Auto resolve conflicts by "ours" strategy option' '
+	git checkout side1^0 &&
+
+	# make sure merge conflict exists
+	test_must_fail git merge side4 &&
+	git merge --abort &&
+
+	git merge -X ours side4 &&
+	git rev-parse HEAD^{tree} >expected &&
+
+	git merge-tree -X ours side1 side4 >actual &&
+
+	test_cmp expected actual
+'
+
 test_expect_success 'Barf on misspelled option, with exit code other than 0 or 1' '
 	# Mis-spell with single "s" instead of double "s"
 	test_expect_code 129 git merge-tree --write-tree --mesages FOOBAR side1 side2 2>expect &&