.editorconfig

fix: new extension for automatically modifying file contents

This change implements most of the corresponding proposal as discussed at the
4.4 and 4.6 sprints: https://www.mercurial-scm.org/wiki/AutomaticFormattingPlan

This change notably does not include parallel execution of the formatter/fixer
tools. It does allow for implementing that without affecting other areas of the
code.

I believe the test coverage to be good, but this is a hotbed of corner cases.

Differential Revision: https://phab.mercurial-scm.org/D2897

# 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