* Link to the commit details on GitHub for a tagged version.
* Non-tagged patches (runtime updates) are still linked to
Google Code because they are identified by a Mercurial commit hash.
- Check for mercurial before using it
- Make 'Merging patches...' wiki page easier to copy
- Use `basename` instead of assuming the user is running vim-patch.sh
via the repo root
- Appease shellcheck by quoting path variables
- Remove unneeded variable quoting inside [[ ]] blocks
- Don't unconditionally 'exit 1'
'-h' and '--help' are both recognized options, so current behavior is
misleading.
