WIP Improve handling of challenging file names when 'core.quotePath=true'

[jmurty]

As described in issue #78 transcrypt could fail to properly handle:

• file names with non-ASCII characters when Git's configuration
  option 'core.quotePath' is set to 'true' (as it is by default)
• file names containing spaces

This change improves handling of non-ASCII or space characters in
filenames and adds a test to exercise and confirm the fix.

Changes in particular:

• fix handling of space characters in file name in pre-commit hook
• override repository's 'core.quotePath' setting in commands that
  output paths to ensure 'core.quotePath=false' is always applied
  even when 'core.quotePath' is explicitly or implicitly (default)
  set to true.

[elasticdog]

This looks good to me...consistently quoting things is always difficult in the realm of Bash. It's a bit ugly to have to manually sprinkle -c core.quotePath=false all over the place, but using -z and handling NUL byte characters probably wouldn't be any better.

Feel free to merge this whenever you're comfortable.

[jmurty]

Thanks for the feedback @elasticdog. I too am unhappy with having -c options sprinkled through the code. I have been thinking through alternatives that still fix the underlying issue, but haven't come up with any great alternatives.

Options I have considered:

1. Forcibly set core.quotePath=false in transcrypt-enabled repositories. This would solve the problem, but in a somewhat aggressive way which might break peoples workflows or tooling. And it seems like a bad idea to override a Git default value like that unless it's really needed.

2. Replace the sprinkled -c overrides with Git aliases which versions that include the -c core.quotePath=false override, e.g: ls-files-unquote, check-attr-unquote, ls-tree-unquote. The transcrypt script would then use these alternatives.

   This is cleaner since it sets the overrides in one place, and works okay in my initial testing except it breaks usage of transcrypt in un-inited repos for actions like transcrypt --list.