diff: when looking for diff configs, support a configurable prefix
In a future commit, I want to make it possible to have the diff options pulled
from (as an example) `commands.commit.interactive.ignorews`; previously we only
supported this for customizable sections (so this would have needed a
`commit-interactive` section and been named `commit-interactive.ignorews`, which
felt a bit weird.
Differential Revision: https://phab.mercurial-scm.org/D5833
# 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