(#38) Ability to ignore merge commits with --maxParents

[llorllale]

PR for #38:

• Adds --max-parents flag (default value of 1), useful for ignoring merge commits

[codecov]

Codecov Report

Merging #42 into master will increase coverage by 1.1%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master      #42     +/-   ##
=========================================
+ Coverage   83.63%   84.74%   +1.1%     
=========================================
  Files           4        4             
  Lines         110      118      +8     
=========================================
+ Hits           92      100      +8     
  Misses          9        9             
  Partials        9        9

Impacted Files	Coverage Δ
internal/commits/commits.go	87.09% <100%> (+1.91%)	⬆️

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