add automation action for plugin_cache.json

[jmartin-tech]

Maintain the distributed plugin_cache.json via github action preformed on merge of PRs to main.

• more tolerant cache validation
  • cache rebuild allows for and empty cache file containing only {}
• new automation action triggered on push to main or manual branch trigger
  • run on push to main
  • only commit when changes are found
  • cancel if a new commit is pushed to same branch including main ( avoids race conditions on cache update )
  • do not commit changes on branch trigger ( only log if changes exist )
  • do not execute when only cache file is updated ( avoids commit loop by automation )

Noted quirks:

• concurrency limit - workflow cancelled by a new commit will mark the commit as failing automation, the subsequent completion will mark only the last push as passing tests
• Commit by automation to main does not trigger a full new test run ( metadata only change makes this reasonable )

[leondz]

Are user caches something that replaces the package cache rather than augmenting it?

[jmartin-tech]

The package cache is a baseline that is immutable on disk to ensure the user does not need write permissions to the install location. The user file is updated from this baseline when it is newer than the user file and augmented with any updates since the package cache was created. This pattern will allow for custom user local items to be added to the cache when that support is added to the project. The user file is utilized exclusively during runtime. It is much less complex to maintain consistency of single cache file than to merge and override sections.

This automation simply forces the user cache file to be built and checks if it is different from the baseline. If it is those change are what needs to be added to the tree since the build is based on the latest commit to the branch.