Specify what files to mutate

Introduction

Currenty it is possible to exclude files. This makes filtering possible so we can specify a few files not to mutate if these for example contain logic that aren’t needed to be tested (like a startup.cs).

Issue

We wish to expand this feature by specifying what files should be mutated. All other files should be excluded. This can be useful on large projects. When a developer made changes in only a few files he could want to do a quick run instead of a full run on all files.

Requirements

• A option --files-to-mutate / -ftm should be added which expects a json array of strings.
• All files not specified should be excluded
• When a folder is specified, all files found in this folder should be mutated
• When a file/folder is specified that is not found a warning should be logged
• When this feature is enabled, file exclusion may not be enabled. Also the other way around.

[royto]

This is the way it is implemented in JS stryker mutator

[rouke-broersma]

Implemented by #662 and released since version 0.13.0