rust-matchers: add `FileMatcher` implementation
Mercurial defines an `exactmatcher`, I find `FileMatcher` to be clearer, but
am not opposed to using the old name.
This change also switched the order of `assert_eq` arguments as it is clearer
that way for most people.
Differential Revision: https://phab.mercurial-scm.org/D7528
# 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