serve(
repos) ->handle,err
Build an http.server handler serving the given repositories read-only
repos maps URL prefixes to repository paths, e.g.
{ ["/lilush"] = "/srv/git/lilush.git" }. Each path must be a git
directory (bare repository) or a worktree containing .git. URLs may
carry an optional .git suffix (clone http://host/lilush.git works).
The returned function matches the http.server handler contract:
handle(method, query, args, headers, body, ctx).