review/git-review: support help when not in git repository

Also use os.Args[0] for binary name.

Change-Id: Ib1b8fc07784c489101e117690a3416baab73f132
Reviewed-on: https://go-review.googlesource.com/1181
Reviewed-by: David Crawshaw <crawshaw@golang.org>
2 files changed
tree: 190634cb0080f415b6b714007aef2ca9d6612ba5
  1. README
  2. git-review/