Ok: this PR is doing score recalculation in 2m 49s vs. 27m 8s on main. That's a pretty nice improvement!

The numbers look really promising! I've given the crate only a cursory read through - it seems like if the goal is to use this for Servo's WPT dashboard, the pending items are

• A way to recalculate past runs by scoring them against a given run.
• Support regex based areas to support /css/CSS2/tables & /css/css-tables. Doesn't have to be regex, I guess, we just need a way to combine arbitrary folders.
• Few unit tests for confidence. Maybe just generating scores.json against a fixed dataset using the crate and diffing it against the current one would also work.

The numbers look really promising! I've given the crate only a cursory read through - it seems like if the goal is to use this for Servo's WPT dashboard, the pending items are

Some up to date numbers: this PR is now calculating in 4m 18s vs 35m 47s for the existing JS version.

• A way to recalculate past runs by scoring them against a given run.

This is now implemented. Unfortunately it is a little slower, but it's not too bad.

• Support regex based areas to support /css/CSS2/tables & /css/css-tables. Doesn't have to be regex, I guess, we just need a way to combine arbitrary folders.

This is implemented as an array of areas to support. Any exact prefix of segment (separated by a /) is supported (/css/, /css/CSS2 and /css/CSS2/tables will all work, but /css/CSS2/tab would not). Currently this is hardcoded into the CLI, but I will probably make it load from the JSON file.

• Few unit tests for confidence. Maybe just generating scores.json against a fixed dataset using the crate and diffing it against the current one would also work.

I have generating identical output to #67 modulo float precision (in the last 2 decimal places of numbers with ~8 decimal places - so I expect this is fine?). This PR is generating a scores.json file and uploading it as an artefact if anyone wishes to compare