connect: annotate refs with their symref information in get_remote_head()

By doing this, clients of upload-pack can now reliably tell what ref
a symbolic ref points at; the updated test in t5505 used to expect
failure due to the ambiguity and made sure we give diagnostics, but
we no longer need to be so pessimistic. Make sure we correctly learn
which branch HEAD points at from the other side instead.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/connect.c b/connect.c
index e4c7ae6e72..553a80c734 100644
--- a/connect.c
+++ b/connect.c
@@ -6,6 +6,7 @@
 #include "run-command.h"
 #include "remote.h"
 #include "url.h"
+#include "string-list.h"
 
 static char *server_capabilities;
 static const char *parse_feature_value(const char *, const char *, int *);
@@ -60,6 +61,61 @@ static void die_initial_contact(int got_at_least_one_head)
 		    "and the repository exists.");
 }
 
+static void parse_one_symref_info(struct string_list *symref, const char *val, int len)
+{
+	char *sym, *target;
+	struct string_list_item *item;
+
+	if (!len)
+		return; /* just "symref" */
+	/* e.g. "symref=HEAD:refs/heads/master" */
+	sym = xmalloc(len + 1);
+	memcpy(sym, val, len);
+	sym[len] = '\0';
+	target = strchr(sym, ':');
+	if (!target)
+		/* just "symref=something" */
+		goto reject;
+	*(target++) = '\0';
+	if (check_refname_format(sym, REFNAME_ALLOW_ONELEVEL) ||
+	    check_refname_format(target, REFNAME_ALLOW_ONELEVEL))
+		/* "symref=bogus:pair */
+		goto reject;
+	item = string_list_append(symref, sym);
+	item->util = target;
+	return;
+reject:
+	free(sym);
+	return;
+}
+
+static void annotate_refs_with_symref_info(struct ref *ref)
+{
+	struct string_list symref = STRING_LIST_INIT_DUP;
+	const char *feature_list = server_capabilities;
+
+	while (feature_list) {
+		int len;
+		const char *val;
+
+		val = parse_feature_value(feature_list, "symref", &len);
+		if (!val)
+			break;
+		parse_one_symref_info(&symref, val, len);
+		feature_list = val + 1;
+	}
+	sort_string_list(&symref);
+
+	for (; ref; ref = ref->next) {
+		struct string_list_item *item;
+		item = string_list_lookup(&symref, ref->name);
+		if (!item)
+			continue;
+		ref->symref = xstrdup((char *)item->util);
+	}
+	string_list_clear(&symref, 0);
+}
+
 /*
  * Read all the refs from the other end
  */
@@ -67,6 +123,7 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 			      struct ref **list, unsigned int flags,
 			      struct extra_have_objects *extra_have)
 {
+	struct ref **orig_list = list;
 	int got_at_least_one_head = 0;
 
 	*list = NULL;
@@ -114,6 +171,9 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 		list = &ref->next;
 		got_at_least_one_head = 1;
 	}
+
+	annotate_refs_with_symref_info(*orig_list);
+
 	return list;
 }