Add git info to context

[b-per]

resolves #8690

Problem

Today, it is not possible to know which branch and/or which commit dbt's current code is based on. This PR adds the variables git_branch and git_sha to the Jinja context

Solution

Add objects to the context

Still To be Done (and keen to get Core Team inputs on the 2 first ones)

• Handle the case where --project-dir is set and not the current dir
• Add tests
• Handle partial parsing gracefully, forcing a full parse if any of the special_override_macros refers to git_branchorgit_sha`.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.61%. Comparing base (d912654) to head (ddd4d0d).
Report is 220 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8693      +/-   ##
==========================================
- Coverage   86.62%   86.61%   -0.01%     
==========================================
  Files         176      176              
  Lines       25663    25696      +33     
==========================================
+ Hits        22230    22257      +27     
- Misses       3433     3439       +6     

Flag	Coverage Δ
integration	83.36% <90.90%> (-0.08%)	⬇️
unit	65.18% <100.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

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

[b-per]

I have now added support for project_dir, updated existing tests and added a new one.

The last pending thing would be to invalidate the partial parsing cache in case git_branch is used there but I would most likely need a bit of help from the core team for that.

[b-per]

Would there also be appetite to add this info to manifest.json and/or run_results.json?

[b-per]

Thinking more about it.

In order to identify that we changed branch (and that we might need to trigger a full parse in case we refer to {{ branch_name }} in one of the generate_xxx_name() ), would there be any other technical way except storing this information in the manifest?

[aranke]

Would there also be appetite to add this info to manifest.json and/or run_results.json?

What would be the use-case here?