Merge branch 'vd/skip-cache-tree-update'

Avoid calling 'cache_tree_update()' when doing so would be redundant.

* vd/skip-cache-tree-update:
  rebase: use 'skip_cache_tree_update' option
  read-tree: use 'skip_cache_tree_update' option
  reset: use 'skip_cache_tree_update' option
  unpack-trees: add 'skip_cache_tree_update' option
  cache-tree: add perf test comparing update and prime

t/helper/test-tool.c

@@ -14,6 +14,7 @@ static struct test_cmd cmds[] = {
 	{ "bitmap", cmd__bitmap },
 	{ "bloom", cmd__bloom },
 	{ "bundle-uri", cmd__bundle_uri },
+	{ "cache-tree", cmd__cache_tree },
 	{ "chmtime", cmd__chmtime },
 	{ "config", cmd__config },
 	{ "crontab", cmd__crontab },