An option to lint whole files instead of changed lines

[Felipe-Kiddom]

Is your feature request related to a problem? Please describe.
when removing code, diff plugin only seems to care about the lines that have changed, and when removing code/cleaning up, the linter doesn't let you know there is an unused variable

Describe the solution you'd like
I think for my use case, it would be sufficient to check an environment variable that has been set CHECK_WHOLE_FILE or something like that