Switch to martinohmann difflib fork and colorize diff output

[kpengboy]

This would at least be a partial solution to #371.

I did not add the colorization to the cfgtest output, but I wonder if I should.

[mbrt]

Do you mind making this optional through a flag?

Some people rely on this in scripts, which would suddenly have garbled logs in them.

To make this nicer, there could be an automatic TTY detection, but this can definitely happen later.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 54.51%. Comparing base (6b9e153) to head (f3f1624).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/engine/label/diff.go	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (50.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #423      +/-   ##
==========================================
- Coverage   54.52%   54.51%   -0.01%     
==========================================
  Files          53       53              
  Lines        4457     4459       +2     
==========================================
+ Hits         2430     2431       +1     
- Misses       1886     1887       +1     
  Partials      141      141              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

This pull request is stale because it has been open for 30 days without activity.
This will be closed in 7 days, unless you add the 'lifecycle/keep-alive' label or comment.

[kpengboy]

keepalive