Reuse build caches where possible

If building a release that has already been built and there's a cache
available for it, skip the rebuild and use the existing cache.  This
means, in particular, that there's no need to repeat a build for a
version-tracking branch after the build has completed on the main
branch.

Author: me-and

.github/workflows/build-test.yml

@@ -90,7 +90,17 @@ jobs:
 
           printf 'pv=%s\n' "$PV" | tee -a "$GITHUB_OUTPUT"
 
+      # Cache hit here means we can skip most of the rest of this job, since
+      # this job is essentially building this cache.
+      - name: Use build cache
+        id: build-cache
+        uses: actions/cache@v3
+        with:
+          key: ${{ env.CYGPORT_NAME }}-build-${{ github.sha }}
+          path: build-results.tar
+
       - name: Install Cygwin build requirements
+        if: steps.build-cache.outputs.cache-hit != 'true'
         uses: cygwin/cygwin-install-action@db475590d56881c6cef7b3f96f6f3dd9532ea1f4
         with:
           packages: ${{ env.CYGPORT_BUILD_REQUIRES }}
@@ -131,64 +141,59 @@ jobs:
           path: C:\cygwin\var\log\
 
       - name: Cygport download
+        if: steps.build-cache.outputs.cache-hit != 'true'
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: cygport "$CYGPORT_FILE" download
 
       - name: Cygport prep
+        if: steps.build-cache.outputs.cache-hit != 'true'
         id: cygport-prep
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: cygport "$CYGPORT_FILE" prep
 
       - name: Cygport compile
+        if: steps.build-cache.outputs.cache-hit != 'true'
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: cygport "$CYGPORT_FILE" compile
 
       - name: Cygport test
+        if: steps.build-cache.outputs.cache-hit != 'true'
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: cygport "$CYGPORT_FILE" test
 
       - name: Cygport install
+        if: steps.build-cache.outputs.cache-hit != 'true'
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: cygport "$CYGPORT_FILE" install
 
       - name: Cygport package
+        if: steps.build-cache.outputs.cache-hit != 'true'
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: cygport "$CYGPORT_FILE" package
 
       - name: Tar up build results
-        if: always()
+        if: always() && steps.cygport-prep.outcome != 'skipped'
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
         env:
           PATH: C:\cygwin\bin
         run: tar -cvf build-results.tar "$CYGPORT_BUILD_DIR"
 
       - name: Store build results
-        if: always() && steps.cygport-prep.outcome == 'success'
+        if: always() && steps.cygport-prep.outcome != 'skipped'
         uses: actions/upload-artifact@v3
         with:
           name: build-results
           path: build-results.tar
           if-no-files-found: error
-
-      # Artifacts are great for letting me download the files, and passing
-      # files between jobs in the same action, but not for passing files
-      # between actions.  Cache the build results so they can be used by a
-      # separate release action.
-      - name: Cache build results
-        if: startsWith(github.ref, 'refs/heads/')
-        uses: actions/cache/save@v3
-        with:
-          key: ${{ env.CYGPORT_NAME }}-build-${{ github.ref_name }}-${{ github.sha }}
-          path: build-results.tar

.github/workflows/prep-release.yml

@@ -121,7 +121,7 @@ jobs:
         id: build-cache
         uses: actions/cache/restore@v3
         with:
-          key: ${{ env.CYGPORT_NAME }}-build-${{ github.ref_name }}-${{ github.sha }}
+          key: ${{ env.CYGPORT_NAME }}-build-${{ github.sha }}
           path: build-results.tar
 
       - name: Abort on cache miss

.github/workflows/release.yml

@@ -105,33 +105,11 @@ jobs:
           printf 'CYGPORT_PF=%s\n' "$PF" | tee -a "$GITHUB_ENV"
           printf 'CYGPORT_ARCH=%s\n' "$ARCH" | tee -a "$GITHUB_ENV"
 
-      - name: Get the release target branch
-        id: target
-        uses: actions/github-script@v6
-        env:
-          TAG_NAME: ${{ inputs.tag_name }}
-        with:
-          script: |
-            const releaseRsp = await github.rest.repos.getReleaseByTag({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              tag: process.env.TAG_NAME
-            });
-            const targetCommitish = releaseRsp.data.target_commitish;
-            if (targetCommitish.startsWith('refs/heads/')) {
-              targetRef = targetCommitish.substring(11);
-            } else if (target_commitish.startsWith('refs/tags/')) {
-              targetRef = targetCommitish.substring(10);
-            } else {
-              core.setFailed('Unexpected target_commitish: ' + targetCommitish);
-            }
-            core.setOutput('target_ref', targetRef);
-
       - name: Get build cache
         id: build-cache
         uses: actions/cache/restore@v3
         with:
-          key: ${{ env.CYGPORT_NAME }}-build-${{ steps.target.outputs.target_ref }}-${{ github.sha }}
+          key: ${{ env.CYGPORT_NAME }}-build-${{ github.sha }}
           path: build-results.tar
 
       - name: Abort on cache miss