- fix gnu stat formatting option from %z to %Z
- use read with a one second timeout instead of sleep, then quit if user
responds with "q" (for testing, mostly)
- call pager_exec on entr and bat line instead of main so that --clear
works
- Add `-h` and `--help` flags to print out basic usage.
- Refactor determine_stat_variant so that it checks to make sure the
value from `stat` is a epoch timestamp, and exit noisily if it is not.
- Change `determine_watcher` to set the `OPT_WATCHER` global directory
directly instead of echoing it then being called from a subshell. There
was an errror that the subshell was obscuring.
- Add a test to reflect the bug.
