.eslintignore rules that start with ! cause nearly all files to be skipped

[blowery]

for example, an .eslintignore with:

!.eslintrc.js

will cause all files to be skipped, because minimatch sees this as a negation rule and matches all files that are not .eslintrc. The intent is the same as .gitignore, "don't skip .eslintrc.js".

Note that eslint does not use minimatch, but instead uses https://www.npmjs.com/package/ignore. See https://github.com/eslint/eslint/blob/master/lib/ignored-paths.js