The load dialog shows the GitHub account state with sign-in, sign-out
and repository-selection links. A clone that needs authorisation shows
a Sign in with GitHub or Grant repository access button, and the
repository is resumed automatically on return from GitHub.
Implements the API routes (jobs, progress events, snapshots, search,
entities, source delivery with release) to net/http and serves the
static frontend from the same binary on the same origin.
Andy Dixon