remote: let's at least pretend to have some memory safety

Copy the pointers into temporary vectors instead of assigning them tot
he same array so we don't mess up with someone else's memory by
accident (e.g. by sorting).

src/remote.c

@@ -719,6 +719,25 @@ static int remote_head_cmp(const void *_a, const void *_b)
 	return git__strcmp_cb(a->name, b->name);
 }
 
+static int ls_to_vector(git_vector *out, git_remote *remote)
+{
+	git_remote_head **heads;
+	size_t heads_len, i;
+
+	if (git_remote_ls((const git_remote_head ***)&heads, &heads_len, remote) < 0)
+		return -1;
+
+	if (git_vector_init(out, heads_len, remote_head_cmp) < 0)
+		return -1;
+
+	for (i = 0; i < heads_len; i++) {
+		if (git_vector_insert(out, heads[i]) < 0)
+			return -1;
+	}
+
+	return 0;
+}
+
 int git_remote_download(git_remote *remote)
 {
 	int error;
@@ -726,12 +745,15 @@ int git_remote_download(git_remote *remote)
 
 	assert(remote);
 
-	if (git_remote_ls((const git_remote_head ***)&refs.contents, &refs.length, remote) < 0)
+	if (ls_to_vector(&refs, remote) < 0)
 		return -1;
 
 	free_refspecs(&remote->active_refspecs);
 
-	if (dwim_refspecs(&remote->active_refspecs, &remote->refspecs, &refs) < 0)
+	error = dwim_refspecs(&remote->active_refspecs, &remote->refspecs, &refs);
+	git_vector_free(&refs);
+
+	if (error < 0)
 		return -1;
 
 	if ((error = git_fetch_negotiate(remote)) < 0)
@@ -980,7 +1002,8 @@ int git_remote_update_tips(git_remote *remote)
 	if (git_refspec__parse(&tagspec, GIT_REFSPEC_TAGS, true) < 0)
 		return -1;
 
-	if ((error = git_remote_ls((const git_remote_head ***)&refs.contents, &refs.length, remote)) < 0)
+
+	if ((error = ls_to_vector(&refs, remote)) < 0)
 		goto out;
 
 	if (remote->download_tags == GIT_REMOTE_DOWNLOAD_TAGS_ALL) {
@@ -997,6 +1020,7 @@ int git_remote_update_tips(git_remote *remote)
 	}
 
 out:
+	git_vector_free(&refs);
 	git_refspec__free(&tagspec);
 	return error;
 }