Merge branch 'bc/credential-scheme-enhancement'
The credential helper protocol, together with the HTTP layer, have
been enhanced to support authentication schemes different from
username & password pair, like Bearer and NTLM.
* bc/credential-scheme-enhancement:
credential: add method for querying capabilities
credential-cache: implement authtype capability
t: add credential tests for authtype
credential: add support for multistage credential rounds
t5563: refactor for multi-stage authentication
docs: set a limit on credential line length
credential: enable state capability
credential: add an argument to keep state
http: add support for authtype and credential
docs: indicate new credential protocol fields
credential: add a field called "ephemeral"
credential: gate new fields on capability
credential: add a field for pre-encoded credentials
http: use new headers for each object request
remote-curl: reset headers on new request
credential: add an authtype field