Factor out logic to exclude sub-modules

[codecov[bot]]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (3b25f39) 42.45067% compared to head (8d53849) 42.50518%. Report is 4 commits behind head on master.

Files	Patch %	Lines
pkg/config/config.go	70.83333%	5 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #761 +/- ## =================================================== + Coverage 42.45067% 42.50518% +0.05451% =================================================== Files 61 61 Lines 4815 4830 +15 =================================================== + Hits 2044 2053 +9 - Misses 2591 2595 +4 - Partials 180 182 +2 ```

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