1 files changed, 71 insertions, 0 deletions
diff --git a/third_party/git/checkout.c b/third_party/git/checkout.c
new file mode 100644
index 000000000000..c72e9f9773e1
--- /dev/null
+++ b/third_party/git/checkout.c
@@ -0,0 +1,71 @@
+#include "cache.h"
+#include "remote.h"
+#include "refspec.h"
+#include "checkout.h"
+#include "config.h"
+
+struct tracking_name_data {
+	/* const */ char *src_ref;
+	char *dst_ref;
+	struct object_id *dst_oid;
+	int num_matches;
+	const char *default_remote;
+	char *default_dst_ref;
+	struct object_id *default_dst_oid;
+};
+
+#define TRACKING_NAME_DATA_INIT { NULL, NULL, NULL, 0, NULL, NULL, NULL }
+
+static int check_tracking_name(struct remote *remote, void *cb_data)
+{
+	struct tracking_name_data *cb = cb_data;
+	struct refspec_item query;
+	memset(&query, 0, sizeof(struct refspec_item));
+	query.src = cb->src_ref;
+	if (remote_find_tracking(remote, &query) ||
+	    get_oid(query.dst, cb->dst_oid)) {
+		free(query.dst);
+		return 0;
+	}
+	cb->num_matches++;
+	if (cb->default_remote && !strcmp(remote->name, cb->default_remote)) {
+		struct object_id *dst = xmalloc(sizeof(*cb->default_dst_oid));
+		cb->default_dst_ref = xstrdup(query.dst);
+		oidcpy(dst, cb->dst_oid);
+		cb->default_dst_oid = dst;
+	}
+	if (cb->dst_ref) {
+		free(query.dst);
+		return 0;
+	}
+	cb->dst_ref = query.dst;
+	return 0;
+}
+
+const char *unique_tracking_name(const char *name, struct object_id *oid,
+				 int *dwim_remotes_matched)
+{
+	struct tracking_name_data cb_data = TRACKING_NAME_DATA_INIT;
+	const char *default_remote = NULL;
+	if (!git_config_get_string_const("checkout.defaultremote", &default_remote))
+		cb_data.default_remote = default_remote;
+	cb_data.src_ref = xstrfmt("refs/heads/%s", name);
+	cb_data.dst_oid = oid;
+	for_each_remote(check_tracking_name, &cb_data);
+	if (dwim_remotes_matched)
+		*dwim_remotes_matched = cb_data.num_matches;
+	free(cb_data.src_ref);
+	free((char *)default_remote);
+	if (cb_data.num_matches == 1) {
+		free(cb_data.default_dst_ref);
+		free(cb_data.default_dst_oid);
+		return cb_data.dst_ref;
+	}
+	free(cb_data.dst_ref);
+	if (cb_data.default_dst_ref) {
+		oidcpy(oid, cb_data.default_dst_oid);
+		free(cb_data.default_dst_oid);
+		return cb_data.default_dst_ref;
+	}
+	return NULL;
+}