fetch: set remote/HEAD if it does not exist

When cloning a repository remote/HEAD is created, but when the user
creates a repository with git init, and later adds a remote, remote/HEAD
is only created if the user explicitly runs a variant of "remote
set-head". Attempt to set remote/HEAD during fetch, if the user does not
have it already set. Silently ignore any errors.

Signed-off-by: Bence Ferdinandy <bence@ferdinandy.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/builtin/fetch.c b/builtin/fetch.c
index c900f57721..b2a36a5d95 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1577,6 +1577,66 @@ static int backfill_tags(struct display_state *display_state,
 	return retcode;
 }
 
+static const char *strip_refshead(const char *name){
+	skip_prefix(name, "refs/heads/", &name);
+	return name;
+}
+
+static int set_head(const struct ref *remote_refs)
+{
+	int result = 0;
+	struct strbuf b_head = STRBUF_INIT, b_remote_head = STRBUF_INIT;
+	const char *remote = gtransport->remote->name;
+	char *head_name = NULL;
+	struct ref *ref, *matches;
+	struct ref *fetch_map = NULL, **fetch_map_tail = &fetch_map;
+	struct refspec_item refspec = {
+		.force = 0,
+		.pattern = 1,
+		.src = (char *) "refs/heads/*",
+		.dst = (char *) "refs/heads/*",
+	};
+	struct string_list heads = STRING_LIST_INIT_DUP;
+	struct ref_store *refs = get_main_ref_store(the_repository);
+
+	get_fetch_map(remote_refs, &refspec, &fetch_map_tail, 0);
+	matches = guess_remote_head(find_ref_by_name(remote_refs, "HEAD"),
+				    fetch_map, 1);
+	for (ref = matches; ref; ref = ref->next) {
+		string_list_append(&heads, strip_refshead(ref->name));
+	}
+
+
+	if (!heads.nr)
+		result = 1;
+	else if (heads.nr > 1)
+		result = 1;
+	else
+		head_name = xstrdup(heads.items[0].string);
+
+	if (!head_name)
+		goto cleanup;
+	strbuf_addf(&b_head, "refs/remotes/%s/HEAD", remote);
+	strbuf_addf(&b_remote_head, "refs/remotes/%s/%s", remote, head_name);
+		/* make sure it's valid */
+	if (!refs_ref_exists(refs, b_remote_head.buf)) {
+		result = 1;
+		goto cleanup;
+	}
+	if (refs_update_symref_extended(refs, b_head.buf, b_remote_head.buf,
+					"fetch", NULL, 1))
+		result = 1;
+
+cleanup:
+	free(head_name);
+	free_refs(fetch_map);
+	free_refs(matches);
+	string_list_clear(&heads, 0);
+	strbuf_release(&b_head);
+	strbuf_release(&b_remote_head);
+	return result;
+}
+
 static int do_fetch(struct transport *transport,
 		    struct refspec *rs,
 		    const struct fetch_config *config)
@@ -1646,6 +1706,8 @@ static int do_fetch(struct transport *transport,
 				    "refs/tags/");
 	}
 
+	strvec_push(&transport_ls_refs_options.ref_prefixes, "HEAD");
+
 	if (must_list_refs) {
 		trace2_region_enter("fetch", "remote_refs", the_repository);
 		remote_refs = transport_get_remote_refs(transport,
@@ -1790,6 +1852,12 @@ static int do_fetch(struct transport *transport,
 				  "you need to specify exactly one branch with the --set-upstream option"));
 		}
 	}
+	if (set_head(remote_refs))
+		;
+		/*
+		 * Way too many cases where this can go wrong
+		 * so let's just fail silently for now.
+		 */
 
 cleanup:
 	if (retcode) {