Replace Gitea cache with sccache setup

README.md

@@ -4,43 +4,68 @@ Reusable Gitea Actions for Rust projects.
 
 ## actions/rust-cache
 
-Composite action that restores Rust build caches, installs a Rust toolchain, and saves updated cargo/rustup/target caches after the job.
+Composite action that installs Rust, installs a prebuilt Mozilla `sccache`
+binary, and configures `RUSTC_WRAPPER=sccache` for later Cargo steps.
 
-### Usage
+This action intentionally does not use Gitea `actions/cache` and does not cache
+`target/`. Rust build artifacts are cached through `sccache`; callers can use
+local sccache storage or an S3-compatible backend.
+
+### S3 usage
+
+Create one shared bucket for Rust compiler artifacts, then pass non-secret S3
+settings as inputs and credentials as normal workflow secrets.
 
 ```yaml
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: https://gitea.com/actions/checkout@v4
+      - uses: actions/checkout@v4
 
-      - name: Setup Rust + Cache
+      - name: Setup Rust + sccache
         uses: https://git.ericxliu.me/eric/actions-rust/.gitea/actions/rust-cache@main
         with:
-          toolchain: stable      # optional, defaults to stable
-          cache-prefix: rust     # optional, defaults to rust
-          cache-version: v3      # optional, defaults to v3
+          toolchain: stable
+          sccache-bucket: sccache
+          sccache-region: auto
+          sccache-endpoint: https://s3.example.com
+          sccache-key-prefix: my-org/my-repo/linux-x64/stable
+        env:
+          AWS_ACCESS_KEY_ID: ${{ secrets.SCCACHE_AWS_ACCESS_KEY_ID }}
+          AWS_SECRET_ACCESS_KEY: ${{ secrets.SCCACHE_AWS_SECRET_ACCESS_KEY }}
 
-      - run: cargo build --release
       - run: cargo test
+      - run: sccache --show-stats
 ```
 
-### What it does
+### Local usage
 
-1. **Cache key** — Hashes root/workspace `Cargo.toml`, `Cargo.lock`, and `rust-toolchain*` files without relying on `hashFiles()`.
-2. **Cache restore/save** — Restores `~/.cargo/registry`, `~/.cargo/git`, `~/.rustup/toolchains`, and `target/` using Gitea's native `actions/cache`. The cache action saves updated paths in its post step after later build/test steps have populated them.
-3. **Rust install** — Runs `rustup` with the minimal profile to install or verify the requested toolchain.
-4. **PATH setup** — Appends `$HOME/.cargo/bin` to `$GITHUB_PATH` so cargo/rustc are available in subsequent steps.
+Omit `sccache-bucket` to use the runner-local sccache cache:
 
-The cache upload is serialized with `CACHE_UPLOAD_CONCURRENCY=1` because Gitea
-act_runner's cache server stores chunk metadata in BoltDB and can return 500s
-under large parallel uploads.
-
-### Cache key format
-
-```
-{cache-prefix}-{cache-version}-{runner.os}-{runner.arch}-{toolchain}-{hash(manifests/toolchain files)}
+```yaml
+- name: Setup Rust + local sccache
+  uses: https://git.ericxliu.me/eric/actions-rust/.gitea/actions/rust-cache@main
+  with:
+    toolchain: stable
 ```
 
-Warm builds run in ~40–60s vs ~3min for a cold build.
+### Inputs
+
+- `toolchain`: Rust toolchain to install. Defaults to `stable`.
+- `sccache`: Set to `"false"` to install Rust without configuring sccache.
+- `sccache-version`: Mozilla sccache release tag. Defaults to `v0.15.0`.
+- `sccache-bucket`: S3 bucket name. Empty means local sccache storage.
+- `sccache-region`: S3 region. For S3-compatible endpoints, `auto` is usually right.
+- `sccache-endpoint`: Optional S3-compatible endpoint URL.
+- `sccache-s3-use-ssl`: Whether the endpoint uses TLS. Defaults to `"true"`.
+- `sccache-s3-enable-virtual-host-style`: Set to `"true"` only for endpoints that require virtual-host-style addressing.
+- `sccache-key-prefix`: Optional cache key prefix. Defaults to repository, runner, and toolchain scope.
+
+### Notes
+
+- Do not pass secret values as action inputs. Pass standard AWS environment
+  variables from workflow secrets.
+- `SCCACHE_IGNORE_SERVER_IO_ERROR=1` is set so a cache outage falls back to
+  local compilation instead of failing the build.
+- Add `sccache --show-stats` after build/test steps to inspect cache hit rates.