sccache (Vercel fork)

This is a Vercel-maintained fork of mozilla/sccache. It is maintained as a stack of patches managed with Graphite, each branch containing a single feature/fix on top of the upstream branch.

For full upstream documentation, see the upstream README or the upstream repository.

Branch structure

• upstream — Tracks mozilla/sccache main. This is the base of the stack.
• vercel/ci-fixes — Bottom of the stack (CI cleanup).
• vercel/multilevel-caching through vercel/fork-readme-ci — Stacked feature branches.
• main — Always points to the top of the stack (same commit as the topmost branch).

Patches

Each patch is a single Graphite branch with one commit. The stack order (bottom to top):

0. CI fixes (vercel/ci-fixes) — Removes coverage, benchmarks, snap, FreeBSD, integration-tests, and unsupported cross-compilation targets from upstream CI.

1. Crate type allow hash (vercel/crate-type-allow-hash) — When SCCACHE_RUST_CRATE_TYPE_ALLOW_HASH is set, all crate types become cacheable. The env var value is hashed into the cache key only when unsupported crate types are present.

2. Rust basedirs (vercel/rust-basedirs) — Strips SCCACHE_BASEDIR prefixes from the Rust hash key so cache entries are portable across machines with different checkout paths.

3. OpenDAL upgrade + Vercel Artifacts backend (vercel/opendal-upgrade-artifacts) — Upgrades opendal via [patch.crates-io] (apache/opendal#7334). Adds Vercel Artifacts cache backend with SCCACHE_VERCEL_ARTIFACTS_TOKEN, _ENDPOINT, _TEAM_ID, _TEAM_SLUG.

4. Reflink-based disk cache (vercel/file-clone-reflink) — Cherry-picked from upstream mozilla/sccache#2640. SCCACHE_FILE_CLONE=true stores entries uncompressed and restores via filesystem reflinks. Drop once merged upstream.

5. File-clone post-write compression (vercel/file-clone-compress) — Adds SCCACHE_FILE_CLONE_COMPRESS to compress reflink entries after write.

6. Directory dep-info hashing (vercel/fix-dir-dep-info) — Fixes mozilla/sccache#2653. Handles directories in rustc dep-info by recursively hashing contents.

7. This README + CI/release workflows + version suffix (vercel/fork-readme-ci) — Fork documentation, vercel-ci.yml, vercel-release.yml, and -vercel suffix on sccache --version.

Previously the stack included a Multi-level caching patch cherry-picked from mozilla/sccache#2581; that PR landed upstream (merge commit d11e2e0) so the fork-specific patch has been dropped.

Managing the stack

This fork uses Graphite to manage the patch stack. Install with npm i -g @withgraphite/graphite-cli.

Viewing the stack

gt log

Modifying a patch mid-stack

gt checkout vercel/<branch-to-edit>
# make changes
git add -A && git commit --amend --no-edit
gt restack                              # rebase all branches above
git checkout vercel/fork-readme-ci      # go to top
git branch -f main HEAD                 # point main at top of stack
git push --force-with-lease origin main vercel/<changed-branch> [other affected branches...]

Adding a new patch to the stack

gt checkout vercel/<branch-below>       # check out where to insert
gt create vercel/<new-branch> -m "commit message"
# make changes
git add -A && git commit -m "description"
gt restack                              # rebase everything above
git checkout vercel/fork-readme-ci
git branch -f main HEAD
git push --force-with-lease origin main vercel/<new-branch> [restacked branches...]

Then create a PR:

gh pr create --base vercel/<branch-below> --head vercel/<new-branch> --title "[N/M] description"

And update the base of the PR that was previously on top of <branch-below>:

gh pr edit <pr-number> --base vercel/<new-branch>

Dropping a merged upstream patch

If an upstream PR (e.g., #2581) gets merged:

gt checkout vercel/<branch-to-drop>
gt move --onto upstream                 # or onto the branch below it
# if the branch is now empty, delete it
gt restack
git checkout vercel/fork-readme-ci
git branch -f main HEAD

Rebasing on latest upstream

git fetch upstream
git checkout upstream
git reset --hard upstream/main          # update the upstream branch
git push --force-with-lease origin upstream
gt restack                              # rebase entire stack
git checkout vercel/fork-readme-ci
git branch -f main HEAD                 # point main at top
git push --force-with-lease origin --all

After any stack modification

Always finish with:

git checkout vercel/fork-readme-ci      # top of stack
git branch -f main HEAD                 # sync main
git push --force-with-lease origin main [affected branches...]

CI & Releases

• vercel-ci.yml — Runs cargo test on Ubuntu and a cargo build --release smoke-check for x86_64-pc-windows-msvc on every push/PR. The Windows job installs Strawberry Perl via shogo82148/actions-setup-perl so openssl-src's Perl build script can run.
• vercel-release.yml — Manual trigger (workflow_dispatch) with an optional version input (defaults to 1.0.YYYYMMDD). Bumps Cargo.toml on a throwaway commit, pushes tag v<version> (not back to main), creates an empty GitHub release, then builds release binaries for x86_64/aarch64 Linux musl, x86_64/aarch64 macOS, and x86_64 Windows. The build matrix is generated via mmastrac/mmm-matrix. Assets are named sccache-<target>.tar.gz (.zip on Windows) and are consumable by cargo binstall.

Installation via cargo binstall

Once a release exists, install the latest prebuilt binary with:

cargo binstall --git https://github.com/vercel/sccache sccache

Cargo.toml ships [package.metadata.binstall] pointing at https://github.com/vercel/sccache/releases/latest/download/sccache-<target>.{tar.gz,zip}, so the command above always pulls the most recent release regardless of the version field in Cargo.toml (which tracks upstream and does not get bumped per release).

Verification

After modifying the stack, verify with:

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

Generate a per-file diff manifest:

for commit in $(git log --reverse --format="%H" upstream..HEAD); do
  echo "### $(git log --oneline -1 $commit)"
  git diff-tree --no-commit-id --name-status -r $commit
  echo
done