QPID-8610: split GitHub Actions caching into /restore and /save (#38)

This implements the https://github.com/actions/cache/blob/main/caching-strategies.md#saving-cache-even-if-the-build-fails

The time savings from caching are significant, especially on Windows CI where caching vcpkg helps a lot.

Author: jiridanek

.github/workflows/build.yml

@@ -91,8 +91,9 @@ jobs:
           sudo chmod +x /usr/bin/sccache
         shell: bash
 
-      - name: Cache scoop (on Windows)
-        uses: actions/cache@v3
+      - name: Cache scoop (restore) (on Windows)
+        uses: actions/cache/restore@v3
+        id: restore-scoop-cache
         if: runner.os == 'Windows'
         with:
           path: ~\scoop
@@ -101,33 +102,18 @@ jobs:
             ${{ runner.os }}-scoop-${{ env.OS_VER }}-
             ${{ runner.os }}-scoop-
 
-      - name: Cache vcpkg/downloads (on Windows)
-        uses: actions/cache@v3
+      - name: Cache vcpkg/downloads and vcpkg/installed (restore) (on Windows)
+        uses: actions/cache/restore@v3
+        id: restore-vcpkg-cache
         if: runner.os == 'Windows'
         with:
-          path: C:\vcpkg\downloads
-          key: ${{ runner.os }}-vcpkg-download-${{ env.OS_VER }}-${{ hashFiles('.github/workflows/build.yml') }}
+          path: |
+            C:\vcpkg\downloads
+            C:\vcpkg\installed
+          key: ${{ runner.os }}-vcpkg-${{ env.OS_VER }}-${{ hashFiles('.github/workflows/build.yml') }}
           restore-keys: |
-            ${{ runner.os }}-vcpkg-download-${{ env.OS_VER }}-
-            ${{ runner.os }}-vcpkg-download-
-      - name: Cache vcpkg/installed (on Windows)
-        uses: actions/cache@v3
-        if: runner.os == 'Windows'
-        with:
-          path: C:\vcpkg\installed
-          key: ${{ runner.os }}-vcpkg-installed-${{ matrix.os }}-${{ hashFiles('.github/workflows/build.yml') }}
-          restore-keys: |
-            ${{ runner.os }}-vcpkg-installed-${{ matrix.os }}-
-            ${{ runner.os }}-vcpkg-installed-
-
-      - name: Cache SCCACHE_DIR
-        uses: actions/cache@v3
-        with:
-          path: "${{ env.SCCACHE_DIR }}"
-          key: ${{ runner.os }}-sccache-${{ matrix.os }}-${{ github.sha }}
-          restore-keys: |
-            ${{ runner.os }}-sccache-${{ matrix.os }}-
-            ${{ runner.os }}-sccache-
+            ${{ runner.os }}-vcpkg-${{ env.OS_VER }}-
+            ${{ runner.os }}-vcpkg-
 
       - name: Install Windows dependencies
         if: runner.os == 'Windows'
@@ -141,13 +127,35 @@ jobs:
 
           # https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#add-a-system-path-add-path
           Add-Content ${env:GITHUB_PATH} "${HOME}/scoop/shims"
-          
+        shell: pwsh
+
+      - name: Cache scoop (save) (on Windows)
+        uses: actions/cache/save@v3
+        if: runner.os == 'Windows'
+        with:
+          path: ~\scoop
+          key: ${{ steps.restore-scoop-cache.outputs.cache-primary-key }}
+
+      - name: Cache vcpkg/downloads and vcpkg/installed (save) (on Windows)
+        uses: actions/cache/save@v3
+        if: runner.os == 'Windows'
+        with:
+          path: |
+            C:\vcpkg\downloads
+            C:\vcpkg\installed
+          key: ${{ steps.restore-vcpkg-cache.outputs.cache-primary-key }}
+
+      # don't save this into the vcpkg cache
+      - name: Copy over Boost DLLs to where we expect them
+        if: runner.os == 'Windows'
+        run: |
           # work around assumptions in our build scripts about boost libs layout
           Copy-Item -Path C:/vcpkg/installed/x64-windows/debug/bin/* -Include *.dll -Destination C:/vcpkg/installed/x64-windows/debug/lib
           Get-Item C:/vcpkg/installed/x64-windows/debug/lib/*.dll | Rename-Item -NewName { $_.Name -replace '-vc14.-mt-gd-x64-1_81.dll','-vc140-mt-gd.dll' }
           # display results of this hard work
           ls C:/vcpkg/installed/x64-windows/debug/bin/
           ls C:/vcpkg/installed/x64-windows/debug/lib/
+
           # now do the same for release
           Copy-Item -Path C:/vcpkg/installed/x64-windows/bin/* -Include *.dll -Destination C:/vcpkg/installed/x64-windows/lib
           Get-Item C:/vcpkg/installed/x64-windows/lib/*.dll | Rename-Item -NewName { $_.Name -replace '-vc14.-mt-x64-1_81.dll','-vc140-mt.dll' }
@@ -156,6 +164,16 @@ jobs:
           ls C:/vcpkg/installed/x64-windows/lib/
         shell: pwsh
 
+      - name: Cache SCCACHE_DIR (restore)
+        uses: actions/cache/restore@v3
+        id: restore-sccache-cache
+        with:
+          path: "${{ env.SCCACHE_DIR }}"
+          key: ${{ runner.os }}-sccache-${{ matrix.os }}-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-sccache-${{ matrix.os }}-
+            ${{ runner.os }}-sccache-
+
       # Windows build should ideally use something like '-G "Visual Studio 16 2019" -A x64',
       #  but -DCMAKE_C_COMPILER_LAUNCHER is only supported by make and ninja generators
       # https://devblogs.microsoft.com/scripting/powertip-line-continuation-in-powershell/
@@ -176,6 +194,12 @@ jobs:
           cmake --install "${{env.BuildDir}}" --config ${{env.BuildType}}
         shell: pwsh
 
+      - name: Cache SCCACHE_DIR (save)
+        uses: actions/cache/save@v3
+        with:
+          path: "${{ env.SCCACHE_DIR }}"
+          key: ${{ steps.restore-sccache-cache.outputs.cache-primary-key }}
+
       - id: ctest
         name: ctest
         working-directory: ${{env.BuildDir}}