feat: change entrypoint to cmd to simplify CI usage

Author: tilaven

.github/workflows/docker.yml

@@ -24,6 +24,10 @@ jobs:
             base_image: alpine:3.20
             rust_target_suffix: musl
             tag_suffix: alpine-3.20
+          - variant: scratch
+            base_image: scratch
+            rust_target_suffix: musl
+            tag_suffix: scratch
           - variant: debian
             base_image: debian:trixie
             rust_target_suffix: gnu
@@ -88,4 +92,4 @@ jobs:
             BASE_IMAGE=${{ matrix.base_image }}
             RUST_TARGET_SUFFIX=${{ matrix.rust_target_suffix }}
           tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
+          labels: ${{ steps.meta.outputs.labels }}

Dockerfile.release

@@ -2,29 +2,20 @@
 ARG ALPINE_VERSION=3.20
 ARG BASE_IMAGE=alpine:${ALPINE_VERSION}
 
-FROM ${BASE_IMAGE}
+FROM alpine:${ALPINE_VERSION} AS prep
 ARG TARGETPLATFORM
 ARG RUST_TARGET_SUFFIX=musl
-RUN set -eux; \
-  if command -v apk >/dev/null 2>&1; then \
-    apk add --no-cache ca-certificates; \
-  elif command -v apt-get >/dev/null 2>&1; then \
-    apt-get update; \
-    DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends ca-certificates; \
-    rm -rf /var/lib/apt/lists/*; \
-  else \
-    echo "Unsupported base image: missing apk/apt-get" >&2; \
-    exit 1; \
-  fi
 COPY dist/ /dist/
-RUN echo "TARGETPLATFORM=${TARGETPLATFORM}"
-RUN case "$TARGETPLATFORM" in \
-  "linux/arm64") echo "aarch64-unknown-linux-${RUST_TARGET_SUFFIX}" > rust_target.txt ;; \
-  "linux/amd64") echo "x86_64-unknown-linux-${RUST_TARGET_SUFFIX}" > rust_target.txt ;; \
-  *) exit 1 ;; \
-  esac
 RUN set -eux; \
-  mv "/dist/diff-coverage-$(cat rust_target.txt)" /usr/local/bin/diff-coverage; \
-  chmod +x /usr/local/bin/diff-coverage; \
-  rm -rf /dist rust_target.txt
-ENTRYPOINT ["diff-coverage"]
+  mkdir -p /out; \
+  case "$TARGETPLATFORM" in \
+    "linux/arm64") target="aarch64-unknown-linux-${RUST_TARGET_SUFFIX}" ;; \
+    "linux/amd64") target="x86_64-unknown-linux-${RUST_TARGET_SUFFIX}" ;; \
+    *) echo "Unsupported TARGETPLATFORM=$TARGETPLATFORM" >&2; exit 1 ;; \
+  esac; \
+  mv "/dist/diff-coverage-${target}" /out/diff-coverage; \
+  chmod +x /out/diff-coverage
+
+FROM ${BASE_IMAGE}
+COPY --from=prep /out/diff-coverage /usr/local/bin/diff-coverage
+CMD ["/usr/local/bin/diff-coverage"]

README.md

@@ -86,6 +86,13 @@ docker run --rm -v "$PWD":/work -w /work tilaven/diff-coverage:<version>-debian-
   coverage.xml --diff-file diff.diff
 ```
 
+Minimal scratch image is available via versioned tags:
+
+```bash
+docker run --rm -v "$PWD":/work -w /work tilaven/diff-coverage:<version>-scratch \
+  coverage.xml --diff-file diff.diff
+```
+
 ## Build
 
 ```bash