[PATCH v3 14/21] read-cache: touch shared index files when used

@@ -1682,6 +1682,19 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	die("index file corrupt");
 }
 
+/*
+ * Signal that the shared index is used by updating its mtime.
+ *
+ * This way, shared index can be removed if they have not been used
+ * for some time. It's ok to fail to update the mtime if we are on a
+ * read only file system.
+ */
+void freshen_shared_index(char *base_sha1_hex)
+{
+	const char *shared_index = git_path("sharedindex.%s", base_sha1_hex);
+	check_and_freshen_file(shared_index, 1);
+}
+
 int read_index_from(struct index_state *istate, const char *path)
 {
 	struct split_index *split_index;

@@ -2273,6 +2286,8 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
 		int ret = write_shared_index(istate, lock, flags);
 		if (ret)
 			return ret;
+	} else {
+		freshen_shared_index(sha1_to_hex(si->base_sha1));
 	}
 
 	return write_split_index(istate, lock, flags);