nearly there; some hardcoded paths need tweaking for push to work

fix issue closing, indicate alpha etc

also setup nixos module

my vision...

The previous cache key was just the path, so files that are often common
across git repos like '.gitignore' etc. show a cached "last commit" time
from another repository. Pretty funny.

This uses the current plumbing.Hash.String():path as the key which
should theoretically be unique to each repository.

Also reduces last time_us discard window down to 2 days.

Restyle commits in repo index and implement a separate commits page with pagination.

I'm bfg'ing this.

Custom lexicon for issues, issue state (open, closed) and issue comments.

The case with issue_at is a bit weird since we have a circular
dependency: the issue record requires the issue_id, and the issue entry
in the db requires the issue_at.

To resolve this we write to the db without the issue_at, fetch the
issue_id, create the issue record on the PDS, and then update the
issue_at (with SetIssueAt). It's not great, but whatever.

also fix nix builds