ci: skip pull request creation when only the analysis cache changes

[ruccho]

Background

The Update Builtin Tasks workflow opened a pull request whenever a new Unity version was detected. However, when a new version introduces no change to the APIs the built-in build tasks depend on, the regenerated Tasks.*.g.cs files are identical to the ones already committed, and the only difference is in AnalysisCache/*.json. A pull request like that contains nothing to review.

In addition, the analysis cache does not reach the default branch until the pull request is merged. If the workflow ran again while the pull request was still open, the same Unity versions were cloned from UnityCsReference and analyzed all over again.

Changes

Evaluate the generated code and the analysis cache separately

A Detect changes step now compares Generated/ and AnalysisCache/ against the default branch independently.

• When the generated code differs, a pull request is created or updated as before.
• When the generated code is unchanged and only the analysis cache differs, no pull request is created. The Commit analysis cache only step commits and pushes the cache alone to the working branch (auto/update-builtin-tasks).

Restore the analysis cache from the working branch

A Restore analysis cache from the working branch step restores only the AnalysisCache directory from the working branch when that branch exists. This lets an open, unmerged pull request still spare the next run from re-analyzing versions that have already been analyzed.

The working branch itself is not checked out — only the cache directory is restored — so the pull request is still opened against the default branch. The restore has to happen before the new-version check (Check for new Unity versions), which is why it is placed immediately above it.

Other

• fetch-depth of actions/checkout is set to 0, since the workflow now commits and pushes to the working branch.
• The branch name and the output directory of the generated code are consolidated into env (BRANCH, GENERATED_DIR).

Notes

peter-evans/create-pull-request rebuilds the branch from the base and force-pushes it. The contents of a cache-only commit are nevertheless preserved, because every run pulls the working branch's cache into the working tree before the generator runs.

Once a pull request is merged the working branch is deleted, and the analysis cache lives on the default branch, so the restore step becomes a no-op.

Verification

The shell scripts embedded in the workflow were checked with bash -n. Actual behavior is expected to be verified by a manual workflow_dispatch run after the merge.

🤖 Generated with Claude Code