make github connector idempotent

[OwenPriceSkelly]

fixes #413

Discussion

This tweaks the trackcalls decorator so that stage can use its own has_been_called attribute and guarantee that it only executes once.

This makes the GH connector behave a little more like the huggingface one by pulling instead of cloning when the directory is already a git repo.

Testing

Wrote a cute little unit test, since it was easy
updated the unit test so it checks that pull is called instead of clone when appropriate

Documentation

no docs

---

📚 Documentation preview 📚: https://garden-ai--417.org.readthedocs.build/en/417/

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 96.55172% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 76.64%. Comparing base (9eb5ba2) to head (fe0a947).

Files	Patch %	Lines
garden_ai/model_connectors/github_conn.py	85.71%	1 Missing ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #417      +/-   ##
==========================================
+ Coverage   76.22%   76.64%   +0.41%     
==========================================
  Files          46       46              
  Lines        2810     2834      +24     
==========================================
+ Hits         2142     2172      +30     
+ Misses        668      662       -6     

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

[WillEngler]

This looks great!