ci: Only save caches on main

This restores caches on all branches and pull requests, but only stores them on the main
branch. This prevents those caches from being evicted early when we hit the 10 GB limit
quickly.

.github/workflows/build.yaml

@@ -114,8 +114,9 @@ jobs:
  runs-on: ${{ matrix.runs-on }}
  steps:
  - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
- - name: Stack working files cache
- uses: actions/cache@ab5e6d0c87105b4c9c2047343972218f562e4319 # v4.0.1.0.1
+ - name: Restore stack working files cache
+ uses: actions/cache/restore@ab5e6d0c87105b4c9c2047343972218f562e4319 # v4.0.1
+ id: restore-cache
  with:
  path: ${{ matrix.cache }}
  key: stack-${{ runner.os }}-${{ hashFiles('stack.yaml.lock') }}
@@ -137,6 +138,12 @@ jobs:
  result/postgrest
  result/postgrest.exe
  if-no-files-found: error
+ - name: Save stack working files cache
+ if: ${{ github.ref == 'refs/heads/main' }}
+ uses: actions/cache/save@v4
+ with:
+ path: ${{ matrix.cache }}
+ key: ${{ steps.restore-cache.outputs.cache-primary-key }}
 
 
  freebsd:
@@ -170,8 +177,9 @@ jobs:
  - name: Fix caching
  run: |
  mkdir ~/.cabal
- - name: Cache
- uses: actions/cache@ab5e6d0c87105b4c9c2047343972218f562e4319 # v4.0.1.0.1
+ - name: Restore cache
+ uses: actions/cache/restore@ab5e6d0c87105b4c9c2047343972218f562e4319 # v4.0.1
+ id: restore-cache
  with:
  path: |
  ~/.cabal/packages
@@ -186,3 +194,12 @@ jobs:
  cabal build --only-dependencies --enable-tests --enable-benchmarks
  - name: Build
  run: cabal build --enable-tests --enable-benchmarks all
+ - name: Save cache
+ if: ${{ github.ref == 'refs/heads/main' }}
+ uses: actions/cache/save@v4
+ with:
+ path: |
+ ~/.cabal/packages
+ ~/.cabal/store
+ dist-newstyle
+ key: ${{ steps.restore-cache.outputs.cache-primary-key }}