Package auth defines an opinionated wrapper around OAuth2.
It hides configurability of base oauth2 library and instead makes a predefined set of choices regarding where the credentials should be stored and how OAuth2 should be used. It makes authentication flows look more uniform across tools that use infra.libs.auth and allow credentials reuse across multiple binaries.
Also it knows about various environments Chrome Infra tools are running under (GCE, Chrome Infra Golo, GAE, developers' machine) and switches default authentication scheme accordingly (e.g. on GCE machine the default is to use GCE metadata server).
All tools that use infra.libs.auth share same credentials by default, meaning a user needs to authenticate only once to use them all. Credentials are cached in ~/.config/chrome_infra/auth/* and reused by all processes running under the same user account.