MechanismFromFlags returns an auth Mechanism based on flags currently set.

UpdateStatus updates ADC credentials status if expired.

ADC is GCP's application default credentials authentication mechanism.

CredentialFile is using service account credentials from a proviced file.

CredentialFileFlag indicates the user authenticate with a credential file.

ExitCodeAppDefCredsAuth is the exit code when there is a failure to authenticate with ADC.

ExitCodeCredsFileAuth is the exit code when there is a failure to authenticate using a credentials file.

ExitCodeExternalTokenAuth is the exit code when there is a failure to authenticate with an external token.

ExitCodeGCECredsAuth is the exit code when there is a failure in GCE credentials.

ExitCodeNoAuth is the exit code when no auth option is specified.

ExitCodeUnknown is the exit code when there is an unknown auth issue.

GCE is authentication using GCE VM service accounts.

None implies that the user will not use authentication.

ServiceNoAuthFlag indicates the user will not use authentication.

Unknown is an unknown auth mechanism.

UseAppDefaultCredsFlag is used to authenticate with application default credentials.

UseExternalTokenFlag indicates the user will authenticate with a provided token.

UseGCECredsFlag indicates the user will authenticate with GCE VM credentials.

Error is an error occured during authenticating or initializing credentials.

Mechanism is a mechanism of authentication to the remote execution service.