hooks: allow Unix style environment variables on external Windows hooks
This will help making common hooks between Windows and non-Windows platforms.
Having to build the shellenviron dict here and in procutil.system() is a bit
unfortunate, but the only other option is to fix up the command inside
procutil.system(). It seems more important that the note about the hook being
run reflects what is actually run.
The patch from last summer added the hooks on the command line, but it looks
like HG_ARGS has since learned about --config args, and the output was just
confusing. Therefore, it's now loaded from a file in the histedit test for
clarity.
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false