Add an option to limit maximum commits used for frecency

[last-partizan]

This adds an option to limit number of processed commits for frecency.

We use number instead of date, because it works the same for both active and not very active repos.

Refs #711

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.91%. Comparing base (587938a) to head (43ccb45).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #756      +/-   ##
==========================================
+ Coverage   89.86%   89.91%   +0.04%     
==========================================
  Files          19       19              
  Lines        1125     1130       +5     
==========================================
+ Hits         1011     1016       +5     
  Misses        114      114              

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

[kantord]

pls just add some unit tests (I guess a test case for "infinte" mode, a test case for a custom limit and a test case for the default limit) and I will approve it

[last-partizan]

Done, please take a look!