docs: Vercel fork README, CI test workflow, and release workflow

Adds .github/README.md with fork-specific documentation including
patch list, rebase workflow instructions for agents, and CI/release
info. This displays over the upstream README.md on GitHub.

Adds vercel-ci.yml (test on push/PR) and vercel-release.yml (manual
workflow_dispatch that builds x86_64 + aarch64 musl binaries and
creates a vercel-YYYYMMDD tagged GitHub release with patch stack).

Removes code coverage (grcov/codecov) and benchmarks (codspeed)
from upstream CI workflows.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mmastrac

.github/README.md

@@ -0,0 +1,65 @@
+# sccache (Vercel fork)
+
+This is a Vercel-maintained fork of [mozilla/sccache](https://github.com/mozilla/sccache). It is maintained as a linear stack of patches (one commit = one feature) on top of the upstream `main` branch.
+
+For full upstream documentation, see the [upstream README](../README.md) or the [upstream repository](https://github.com/mozilla/sccache#readme).
+
+## Patches
+
+Each patch is a single commit. Generate the current patch list with:
+
+```
+git log --oneline upstream/main..HEAD
+```
+
+Current patches (oldest first):
+
+1. **Multi-level caching with automatic backfill** — Cherry-picked from upstream [mozilla/sccache#2581](https://github.com/mozilla/sccache/pull/2581). Adds hierarchical cache storage (e.g., disk -> redis -> s3) with configurable write tolerance policies and automatic backfill from slower tiers. Drop this patch once the PR is merged upstream.
+
+2. **Allow caching all Rust crate types via `SCCACHE_RUST_CRATE_TYPE_ALLOW_HASH`** — Vercel-originated patch. When this env var is set, all crate types (bin, dylib, cdylib, proc-macro) become cacheable. The env var value is hashed into the cache key only when unsupported crate types are present, so machines with different linker setups get separate cache entries.
+
+3. **Upgrade opendal + Vercel Artifacts cache backend** — Upgrades opendal to [mmastrac/opendal vercel_opts](https://github.com/mmastrac/opendal/tree/vercel_opts) branch via `[patch.crates-io]` ([apache/opendal#7334](https://github.com/apache/opendal/pull/7334)). Adds `layers-logging` feature and `aws-lc-sys/prebuilt-nasm`. Adds Vercel Artifacts cache backend configured via `SCCACHE_VERCEL_ARTIFACTS_TOKEN`, plus optional `SCCACHE_VERCEL_ARTIFACTS_ENDPOINT`, `SCCACHE_VERCEL_ARTIFACTS_TEAM_ID`, `SCCACHE_VERCEL_ARTIFACTS_TEAM_SLUG`. Once the upstream opendal PR merges, switch the patch to `apache/opendal` main. Drop the patch entirely once opendal publishes a release with these changes.
+
+4. **This README + CI/release workflows** — Fork documentation, CI test workflow, and release workflow.
+
+## CI & Releases
+
+- **`vercel-ci.yml`** — Runs `cargo test` on Ubuntu on every push/PR.
+- **`vercel-release.yml`** — Manual trigger (`workflow_dispatch`). Builds static musl binaries for `x86_64` and `aarch64` Linux, then creates a GitHub release tagged `vercel-YYYYMMDD` with the patch stack in the release description.
+
+## Agent instructions for rebasing on upstream
+
+When rebasing this fork on the latest upstream `main`, follow these steps:
+
+1. **Set up the upstream remote** (one-time):
+   ```
+   git remote add upstream https://github.com/mozilla/sccache.git
+   ```
+
+2. **Fetch upstream and rebase**:
+   ```
+   git fetch upstream
+   git rebase upstream/main
+   ```
+   This replays each patch commit on top of the latest upstream.
+
+3. **Resolve conflicts patch-by-patch**. For each patch that conflicts:
+   - Fix the conflict in the affected files
+   - `git add <files>` and `git rebase --continue`
+   - Build and run tests to confirm correctness: `cargo build && cargo test`
+   - If a patch corresponds to an upstream PR that has been merged (e.g., #2581), it will likely produce an empty commit or trivial conflict — **drop it** with `git rebase --skip` or remove it during interactive rebase
+
+4. **Update this README**: revise the patch list above to reflect any dropped or added patches. Regenerate with `git log --oneline upstream/main..HEAD`.
+
+5. **Run formatting, lints, build, and tests** after all patches are applied:
+   ```
+   cargo fmt --all
+   cargo clippy --locked --all-targets -- -D warnings -A unknown-lints -A clippy::type_complexity -A clippy::new-without-default
+   cargo build
+   cargo test
+   ```
+
+6. **Force-push** the rebased branch:
+   ```
+   git push --force-with-lease origin main
+   ```

.github/workflows/benchmarks.yml

@@ -118,14 +118,8 @@ jobs:
             rustc: beta
             notest_cuda_compilers: clang++
             extra_desc: cuda12.8
-            no_coverage: true
     env:
       RUST_BACKTRACE: 1
-      COVERAGE_REPORT_DIR: "target/debug"
-      COVERAGE_REPORT_FILE: "target/debug/lcov.info"
-      BINARY_DIR: "target/debug"
-      GRCOV_IGNORE_OPTION: '--ignore build.rs --ignore "/*" --ignore "[a-zA-Z]:/*"'
-      GRCOV_EXCLUDE_OPTION: '--excl-br-line "^\s*((debug_)?assert(_eq|_ne)?!|#\[derive\()"'
       NOTEST_CUDA_COMPILERS: ${{ matrix.notest_cuda_compilers || '' }}
       CARGO_PROFILE_DEV_DEBUG: '0' # save disk space
     steps:
@@ -139,7 +133,6 @@ jobs:
         uses: ./.github/actions/rust-toolchain
         with:
           toolchain: ${{ matrix.rustc }}
-          components: llvm-tools-preview
 
       - if: ${{ contains(matrix.os, 'ubuntu') }}
         name: Install gcc & clang for tests
@@ -164,39 +157,6 @@ jobs:
         with:
           cuda-version: ${{ matrix.cuda }}
 
-      - name: "`grcov` ~ install"
-        if: ${{ ! matrix.no_coverage }}
-        shell: bash
-        run: |
-          GRCOV_VERSION="0.10.7"
-          if [[ "$RUNNER_OS" == "Windows" ]]; then
-            TARGET="x86_64-pc-windows-msvc"
-            EXT="zip"
-          elif [[ "$RUNNER_OS" == "macOS" && "$RUNNER_ARCH" == "ARM64" ]]; then
-            TARGET="aarch64-apple-darwin"
-            EXT="tar.bz2"
-          elif [[ "$RUNNER_OS" == "macOS" ]]; then
-            TARGET="x86_64-apple-darwin"
-            EXT="tar.bz2"
-          else
-            TARGET="x86_64-unknown-linux-musl"
-            EXT="tar.bz2"
-          fi
-          URL="https://github.com/mozilla/grcov/releases/download/v${GRCOV_VERSION}/grcov-${TARGET}.${EXT}"
-          curl -sL "$URL" -o "grcov.${EXT}"
-          if [[ "$EXT" == "zip" ]]; then
-            unzip -q "grcov.${EXT}" -d "$HOME/.cargo/bin/"
-          else
-            tar -xjf "grcov.${EXT}" -C "$HOME/.cargo/bin/"
-          fi
-
-      - name: Create config for testing
-        if: ${{ ! matrix.no_coverage }}
-        run: |
-          mkdir -p .cargo
-          echo '[env]
-          LLVM_PROFILE_FILE = { value = "target/debug/coverage/default-%p-%8m.profraw", relative = true }' >> .cargo/config.toml
-
       - if: ${{ matrix.cuda != '' && runner.os == 'Linux' }}
         name: Free disk space for CUDA tests
         run: |
@@ -208,45 +168,13 @@ jobs:
         env:
           CARGO_INCREMENTAL: "0"
           RUSTC_WRAPPER: ""
-          RUSTFLAGS: "-Cinstrument-coverage -Ccodegen-units=1 -Copt-level=0 -Coverflow-checks=off"
 
       - name: Upload failure
         if: failure()
         uses: ./.github/actions/artifact_failure
         with:
           name: test-${{ matrix.os }}-${{ matrix.rustc || 'stable' }}-${{ matrix.extra_desc }}
 
-  # coverage:
-      - name: Display coverage files
-        if: ${{ ! matrix.no_coverage }}
-        shell: bash
-        run:
-          grcov . -s . --binary-path $BINARY_DIR --output-type files $GRCOV_IGNORE_OPTION $GRCOV_EXCLUDE_OPTION | sort --unique
-
-      - name: Generate coverage data (via `grcov`)
-        if: ${{ ! matrix.no_coverage }}
-        id: coverage
-        shell: bash
-        run: |
-          mkdir -p "${COVERAGE_REPORT_DIR}"
-          grcov . -s . --binary-path $BINARY_DIR --output-type lcov --output-path "${COVERAGE_REPORT_FILE}" --branch $GRCOV_IGNORE_OPTION $GRCOV_EXCLUDE_OPTION
-          echo "report=${COVERAGE_REPORT_FILE}" >> $GITHUB_OUTPUT
-
-      - name: Upload coverage results (to Codecov.io)
-        if: ${{ ! matrix.no_coverage }}
-        uses: codecov/codecov-action@v5
-        with:
-          files: ${{ steps.coverage.outputs.report }}
-          ## flags: IntegrationTests, UnitTests, ${{ steps.vars.outputs.CODECOV_FLAGS }}
-          flags: ${{ steps.vars.outputs.CODECOV_FLAGS }}
-          name: codecov-umbrella-${{ matrix.os }}-rust_${{ matrix.rustc || 'stable' }}-${{ matrix.extra_desc }}
-          fail_ci_if_error: true
-          # verbose: true
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
-
-
-
   build:
     name: build ${{ matrix.binary || 'sccache' }} ${{ matrix.target }}
     runs-on: ${{ matrix.os }}

.github/workflows/ci.yml

@@ -44,26 +44,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Test
-        run: cd tests/integration && WITH_COVERAGE=1 make test-${{ matrix.type }}
-
-      - name: Build report
-        run: |
-          cd tests/integration
-          WITH_COVERAGE=1 make coverage-report
-          echo "Coverage files:"
-          ls ../../target/integration-coverage/profraw -l
-          echo "Coverage report:"
-          ls ../../target/integration-coverage/reports/lcov.info -l
-
-      - name: Upload coverage results (to Codecov.io)
-        uses: codecov/codecov-action@v5
-        with:
-          files: target/integration-coverage/reports/lcov.info
-          name: codecov-umbrella-integration-${{ matrix.type }}
-          fail_ci_if_error: true
-          # verbose: true
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+        run: cd tests/integration && make test-${{ matrix.type }}
 
   gha:
     runs-on: ubuntu-24.04

.github/workflows/integration-tests.yml

@@ -0,0 +1,35 @@
+name: vercel-ci
+on: [push, pull_request]
+
+jobs:
+  test:
+    name: test ubuntu
+    runs-on: ubuntu-22.04
+    timeout-minutes: 30
+    env:
+      RUST_BACKTRACE: 1
+      CARGO_INCREMENTAL: "0"
+      RUSTC_WRAPPER: ""
+      CARGO_PROFILE_DEV_DEBUG: "0"
+    steps:
+      - name: Clone repository
+        uses: actions/checkout@v5
+
+      - name: Install rust
+        uses: ./.github/actions/rust-toolchain
+        with:
+          toolchain: stable
+
+      - name: Install gcc & clang for tests
+        env:
+          DEBIAN_FRONTEND: noninteractive
+        run: |
+          set -x
+          if dpkg -s gcc-14 >/dev/null 2>&1; then
+            sudo apt remove -y gcc-14 g++-14
+            sudo apt autoremove -y
+          fi
+          sudo apt install -y --no-install-recommends gcc clang
+
+      - name: Execute tests
+        run: cargo test --locked --lib --bins --tests