Performance fix: lazier download of repodata

[dwhswenson]

This pull request refactors the CondaReleaseSource class in src/spec0/releasesource.py to introduce a caching mechanism for repository data, enhancing performance by delaying the download until needed. The key changes include replacing the _repodata attribute with a cached property and updating related logic to utilize this cache.

Refactoring and Performance Improvements:

• Introduced a _repodata_cache attribute and a _repodata property to manage repository data caching. This ensures that repository data is only fetched and processed once, improving efficiency.
• Updated the logic for merging package data to use the _repodata_cache instead of directly modifying the _repodata attribute. This change aligns with the new caching mechanism.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.30%. Comparing base (40a0bf7) to head (cc6a544).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #12   +/-   ##
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  Coverage   99.29%   99.30%           
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  Files          15       15           
  Lines         853      859    +6     
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+ Hits          847      853    +6     
  Misses          6        6           

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[Copilot]

Pull Request Overview

This PR refactors CondaReleaseSource to lazily fetch and cache repository data, improving performance by avoiding redundant downloads.

• Added a _repodata_cache attribute and replaced direct _repodata assignment with a lazy-loaded @property.
• Updated merge loops to populate the cache instead of modifying the attribute directly.
• Maintained existing merge logic while deferring network and file operations until first access.

Comments suppressed due to low confidence (1)

src/spec0/releasesource.py:269

• Add unit tests for the _repodata property to verify that repodata is fetched only once and that subsequent accesses return the cached result.

self._repodata_cache = None

[Copilot]

[nitpick] Consider using functools.cached_property instead of a manual cache to simplify the implementation and reduce boilerplate.

[dwhswenson]

hmm... I hadn't been aware of that. Nice trick to know, but I don't think I'll use it here. We might invalidate this cache at some point, and that's considerably uglier and less obvious with a functools.cached_property (you have to delete the entry from the instance's __dict__, as opposed to setting self._cache = None)

[ethanholz]

LGTM merging