Show github changes between actual and previous run

[joanhey]

First we added a link to the commit tree #3 of each run.

Now we can add the changes from one run to another.
Really useful to see the changes in github when results change.

compare/{actual-commit-id}...{previous-commit-id}

Example:
TechEmpower/FrameworkBenchmarks@b6bcbba...1e29786

This show the changes from the actual run vs the previous worked run.

[michaelhixson]

Sounds reasonable. It emails us this link when the final zip file for a run is uploaded, so the logic for this is buried in UploadResultsHandler. I can move that logic into a place where the results details page can use it too.