dist: tools: git-cache: update README

dist/tools/git/README.md

@@ -5,21 +5,19 @@ This directory contains some git tools used by RIOT's build system
 ## git-cache
 
 Simple git caching script, from https://github.com/kaspar030/git-cache
-If git-cache is unconfigured, the script pulls from the given remote location.
+If git-cache has not been initialized, it will fall back to do checkouts from
+the remote repository.
+Otherwise it will transparently cache repositories in it's cache folder,
+ideally not touching the network if a requested commit / tag can be cloned from
+the cache.
 
 In order to set up the cache, do:
 
 - install the git-cache binary into path.
   This will make the script available as "git cache ...".
   Alternatively, directly execute it.
-- run "git cache init", which initializes a git cache in ${HOME}/.gitcache.
+- run "git cache init" (or "dist/tools/git/git-cache init", which initializes a
+  git cache in ${HOME}/.gitcache.
   The used path can be overridden using the "GIT_CACHE_DIR" environment
   variable.
   The cache repository will be used to cache multiple remote repositories.
-- add a repository to the cache: "git cache add \<URL\>
-- whenever needed (at least once after adding a repository),
-  run "git cache update"
-
-If the GIT_CACHE_AUTOADD environment variable is set to "1", a "git cache
-clone" will add the repository to the cache (and immediately update) if the url
-is not yet in the cache.