Exclude specified paths from mutants generation

[dmoka]

I believe that it would be handy to exclude specified paths from the mutants generation.

Let's say that I want to exclude things like configuration logic or some test helper logic files, located within the src directory. Right now the default behaviour of cargo mutants command is that it tries to generate mutants for every file in the src directory and in their child directories.

I could envision having a command line parameter as follows:

cargo mutants --exclude <regexes-for-paths-to-be-excluded>

Use case scenario:

Prerequisite:

Git clone test repo

Steps:

1. Go to the main directory of the cloned repo
2. Execute the following command

cargo mutants --exclude "(\/src\/tests)" "(\/src\/config)"

Expected behaviour:

Every file which is located in either /src/tests or /src/config directories are excluded from mutants generation.

Actual behaviour:

Because of the default behaviour of cargo-mutants (and due to the non-existency of this command line parameter) there are mutants generated for the files both in /src/tests and /src/config

[sourcefrog]

Yep. There is already -f to say which files you do want to test. We could usefully and easily add the opposite. I think it should be a glob (as -f is) not a regexp.

[dmoka]

You are right, glob is indeed a much better one for paths.

I believe that it would be a nice first-issue for me, would be glad to pick this task up. Is it fine by you?

[sourcefrog]

That would be great, thanks! You should be able to work off the existing -f implementation.

[dmoka]

PR has been created, ready to be reviewed