enhance freeze and clone for groups

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 43.33333% with 17 lines in your changes are missing coverage. Please review.

Project coverage is 85.39%. Comparing base (1b6319b) to head (b126c24).

Files	Patch %	Lines
gita/io.py	28.57%	10 Missing :warning:
gita/__main__.py	53.33%	7 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #272 +/- ## ========================================== - Coverage 86.30% 85.39% -0.91% ========================================== Files 5 6 +1 Lines 796 815 +19 ========================================== + Hits 687 696 +9 - Misses 109 119 +10 ```

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