A bare `git fetch origin` (and `git fetch upstream`) pulls every ref. The
repo carries thousands of auto-generated branches, so on any
non-single-branch checkout the installer's update path and `hermes update`
spend minutes downloading the full branch list — long enough to stall the
desktop installer or trip the follow-up `git pull --ff-only`.
Scope every update-path fetch to the branch we actually compare/merge
against:
- scripts/install.sh: collapse the remote to single-branch and fetch only
$BRANCH on the "existing install, updating" path.
- hermes_cli/main.py: fetch the resolved branch in the apply path, the
--check path (upstream + origin), and the fork upstream-sync.
Tracking-ref updates still happen via git's opportunistic refspec, so the
later origin/<branch> rev-parse/rev-list checks are unaffected.
Tests assert the apply-path fetch is branch-scoped and never bare.