Fix the order in which the infection configuration files are loaded

[theofidry]

The expected order is:

• custom file if specified
• infection.json file if available
• infection.json.dist file

[tests-checker]

Thank you for contributing to Infection. We noticed you didn't add any tests. Could you please add them to make sure everything works as expected?

[maks-rafalko]

I guess this is BC break. Nothing bad here as we are on 0.x, but let's mark such issues so that we can list it on the blog post for 0.16 version / changelog

[theofidry]

Fair

[sanmai]

This isn’t a BC break, it’s a bug fix. Hard to BC break something that wasn’t working.

[maks-rafalko]

Why so? If you had 2 files (with and without .dist) and they had different content, they will be swapped right now, no?

[sanmai]

If you had infection.json before together with infection.json.dist the first was never ever considered. Contrary to what supposed to happen according to the manual.

You can commit it to the VCS and, if necessary, override it locally by creating infection.json which should be ignored (e.g. in .gitignore).

I wish this was tested somehow.

[maks-rafalko]

If you had infection.json before together with infection.json.dist the first was never ever considered.

right, and now (after this PR) it will be considered.

[sanmai]

Right, means I'm wrong that this isn't a BC break. It is both bug fix and BC break.

[maks-rafalko]

Exactly. Thanks ;)