The existing version.txt is kinda annoying. The common case of referring
to the current version requires joining three values and the names of
those values only make sense in ChromeOS. Instead just use version as a
string, using VERSION, VERSION_ID, and BUILD_ID just as they appear in
os-release. It is up to the few scripts that need the individual parts
to break the version apart.
The old values remain for the sake of compatibility.
- it shouldn't be possible to set the SDK version to the same as the new
tag's version. The SDK must always be a previous build.
- don't fail if there isn't any old manifests to git rm.
There are ways to improve, it'd be sexy if it was truly safe and we
could throw around annoying terms like idempotent to make this kind of
sequence just work but doesn't yet: tag_release; tag_release --push
A number of places refer to these paths and that number is going to
grow. Since the standard pattern is to use environment variables for
commonly used paths it is time to add ones for these:
REPO_CACHE_DIR
REPO_MANIFESTS_DIR
