hasUncommitted shells out to git and can throw; release() now catches that
inside a try/finally so notifyReleased and launcher.stop always run, and
defaults to preserving the worktree on a throw (can't tell dirty vs clean,
so don't risk deleting unrecoverable work). reapIdle wraps each per-session
release in try/catch, matching drainAll, so one bad session no longer
skips the rest of the reaping pass.
Dai Ha
8fd2d7e5e7