refs: propagate EEXISTS upon renaming

src/refs.c

@@ -1357,8 +1357,8 @@ int git_reference_rename(git_reference *ref, const char *new_name, int force)
 		normalization_flags) < 0)
 			return -1;
 
-	if (reference_can_write(ref->owner, normalized, ref->name, force) < 0)
-		return -1;
+	if ((result = reference_can_write(ref->owner, normalized, ref->name, force)) < 0)
+		return result;
 
 	/* Initialize path now so we won't get an allocation failure once
 	 * we actually start removing things. */

tests-clar/refs/rename.c

@@ -337,3 +337,14 @@ void test_refs_rename__move_up(void)
     git_reference_free(ref);
     git_reference_free(looked_up_ref);
 }
+
+void test_refs_rename__propagate_eexists(void)
+{
+	git_reference *ref;
+
+	cl_git_pass(git_reference_lookup(&ref, g_repo, packed_head_name));
+
+	cl_assert_equal_i(GIT_EEXISTS, git_reference_rename(ref, packed_test_head_name, 0));
+
+	git_reference_free(ref);
+}