ccache in GitHub Actions is likely ineffective for master

[TimWolla]

Description

The cache key for GitHub is configured as:

key: "LINUX_X64_${{ matrix.debug && 'DEBUG' || 'RELEASE' }}_${{ matrix.zts && 'ZTS' || 'NTS' }}${{ matrix.asan && '_ASAN' || '' }}-${{hashFiles('main/php_version.h')}}"

Because GitHub’s caches are immutable (on a hit, the cache will not be updated), and because master’s php_version.h changes rarely, ccache is currently using a 9 month old cache, as per https://github.com/php/php-src/actions/caches. A 9 month old cache might as well not exist.

The cache should regularly be regenerated, e.g. by embedding the current week within the cache key and then configuring restore keys with a common prefix that allows everything, no matter the week:

    - id: week
      run: |
        echo "week=$(date +"%Y-%W")" >> $GITHUB_OUTPUT

      - name: ccache
        uses: hendrikmuhs/ccache-action@v1.2
        with:
          # This duplicates the "job.name" expression above because
          # GitHub has no way to query the job name (github.job is the
          # job id, not the job name)
          key: "LINUX_X64_${{ matrix.debug && 'DEBUG' || 'RELEASE' }}_${{ matrix.zts && 'ZTS' || 'NTS' }}${{ matrix.asan && '_ASAN' || '' }}-${{hashFiles('main/php_version.h')}}-${{ steps.week.outputs.week }}"
          restore-keys: |
            LINUX_X64_${{ matrix.debug && 'DEBUG' || 'RELEASE' }}_${{ matrix.zts && 'ZTS' || 'NTS' }}${{ matrix.asan && '_ASAN' || '' }}-${{hashFiles('main/php_version.h')}}-
          append-timestamp: false

Alternatively append-timestamp could be configured as true, which would update the caches for every build.

PHP Version

n/a

Operating System

No response