Report directory structure when comparing branches seems off

When running rubycritic in CI mode, the report-folder seems to be weirdly nested.

After executing the following command (while on a branch called test-123):

$ rubycritic --mode-ci=develop --format=json app

I get the following directory structure:

tmp/rubycritic/
├── build_number.txt
└── compare
    ├── build_details.txt
    └── develop
        ├── compare
        │   └── test-123
        │       ├── compare
        │       │   └── report.json
        │       └── report.json
        └── report.json

I would expect the structure to be this:

tmp/rubycritic/
├── build_number.txt
└── compare
    ├── build_details.txt
    ├── develop
    │   └── report.json
    ├── test-123
    │   └── report.json
    └── report.json

Actually, when generating a HTML report, the links in the top right corner also seem to expect this structure.

I am happy to create a PR for this, jut wanted to confirm first if this is an actual issue. I think the problem is that Config.root is overwritten in two places during the branch comparison and not reset to its initial value: here and here.

While at it, I have two additional questions regarding the CI mode (happy to create separate issues if preferred):

• The help (and also the readme) states that the CI mode will be faster. This currently seems to not be the case, as it runs a full analysis of both branches, and then looks at the diff. So it's about twice as slow as the normal run. Maybe I am doing something wrong (see command above)?
• Wouldn't it make more sense to include the information stored in build_details.txt in the json output, so that it can be easily parsed?

Reproduce the CI comparison with rubycritic --mode-ci=develop --format=json app and inspect lib/rubycritic/commands/compare.rb, especially the linked lines 52 and 60 where Config.root is changed. Compare the generated report paths with the expected tmp/rubycritic/compare layout and verify that the HTML links resolve to the same structure.