fix: warn when a fixer doesn't have a configured command
It seems we currently produce an empty command line and then decide to
not run it, but it seems better to skip that part too.
Differential Revision: https://phab.mercurial-scm.org/D7085
# 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