Don't capture false positives

[adamvonbaron]

this is a pr to resolve #743. upon thinking about the cause of this problem more i realized that the output causing the false positive was output emitted by yarn. my initial thought was to write a regex that would capture output that was yarn specific and ignore it, however this makes several assumptions about how other people may be using overcommit. i think it can be much more simple than that. the regex used to capture eslint messages here:

overcommit/lib/overcommit/hook/pre_commit/es_lint.rb

Line 33 in 6b25f5d

/^(?<file>(?:\w:)?[^:]+):[^\d]+(?<line>\d+).*?(?<type>Error|Warning)/,

actually does a really good job at capturing the data needed for overcommit to output information and adding a small tweak to that rule fixes the issue at hand. eslint messages have no whitespace before a file or filepath that has a linting issue, but something like

$ yarn eslint --quiet --format=compact /app/project/Error.ts

does. if we can just simply ignore any lines that DO have whitespace before the <file> capture group we can presume that line is not an eslint error or warning message, but some output emitted by some other program (such as yarn).

[sds]

Thank you!