refactor(dockerfile): rewrite using debian-slim as base image

- DART does not seem to work on Alpine
- use Debian-slim base instead
- change to entrypoint/cmd structure
- pass cmd as shell script instead of JSON for now

Dockerfile

@@ -1,36 +1,47 @@
 #
-# Dart-SASS compiler on Alpine
+# Dart-SASS compiler on Debian-Slim
 #
 
-ARG ALPINE_VERSION=3.14
+ARG DEBIAN_VERSION=buster-slim
-FROM alpine:${ALPINE_VERSION}
+FROM debian:${DEBIAN_VERSION}
-ARG ALPINE_VERSION
+ARG DEBIAN_VERSION
-ARG SASS_VERSION=1.35.1
+ARG SASS_VERSION=1.36.0
 
 # create a limited user to run sass
 ARG SASS_UID=8101
 ARG SASS_GID=8101
-RUN addgroup -g ${SASS_GID} -S sass \
+RUN addgroup --system --gid ${SASS_GID} sass \
-    && adduser -S -u ${SASS_UID} -G sass -H -g 'sass system user' sass \
+    && adduser \
-    && mkdir -p /sass/sass /sass/css \
+        --system \
-    && chown -R sass:sass /sass
+        --uid ${SASS_UID} \
+        --ingroup sass \
+        --disabled-password \
+        --no-create-home \
+        --gecos 'sass system user' \
+        sass \
+    && mkdir /sass /css \
+    && chown -R sass:sass /sass /css
 
 # download dart-sass, tini and timezone support, update all packages
-RUN apk --update --no-cache add \
+RUN apt-get update \
+    && apt-get install -y \
         tini \
         tzdata \
-    && apk --update --no-cache upgrade \
+        wget \
+    && apt-get upgrade \
+    && rm -rf /var/lib/apt/lists/* \
     && wget https://github.com/sass/dart-sass/releases/download/${SASS_VERSION}/dart-sass-${SASS_VERSION}-linux-x64.tar.gz \
         -O /tmp/dart-sass-${SASS_VERSION}.tar.gz \
-    && tar -zxvf /tmp/dart-sass-${SASS_VERSION}.tar.gz dart-sass/sass -C /usr/local/bin/ --strip-components=1 \
+    && tar -zxvf /tmp/dart-sass-${SASS_VERSION}.tar.gz -C /opt/ \
-    && chmod +x /usr/local/bin/sass
+    && rm -f /tmp/dart-sass-${SASS_VERSION}.tar.gz \
+    && chmod +x /opt/dart-sass/sass
 
 # labels
 MAINTAINER Asif Bacchus <asif@asifbacchus.dev>
 LABEL maintainer="Asif Bacchus <asif@asifbacchus.dev>"
 LABEL dev.asifbacchus.docker.internalName="ab-dart-sass"
 LABEL org.opencontainers.image.authors="Asif Bacchus <asif@asifbacchus.dev>"
-LABEL org.opencontainers.image.description="Dockerized implementation of Dart-SASS compiler running on Alpine Linux using a limited account."
+LABEL org.opencontainers.image.description="Dockerized implementation of Dart-SASS compiler running on Debian (slim) using a limited account."
 LABEL org.opencontainers.image.documentation="https://git.asifbacchus.dev/ab-docker/dart-sass/raw/branch/master/README.md"
 LABEL org.opencontainers.image.source="https://git.asifbacchus.dev/ab-docker/dart-sass.git"
 LABEL org.opencontainers.image.title="ab-dart-sass"
@@ -38,13 +49,14 @@ LABEL org.opencontainers.image.url="https://git.asifbacchus.dev/ab-docker/dart-s
 LABEL org.opencontainers.image.vendor="Asif Bacchus"
 
 # default environment variables
+ENV PATH=$PATH:/opt/dart-sass
 ENV TZ=Etc/UTC
 ENV SASS_STYLE=compressed
 
 # switch to user account and run sass compiler
 USER sass
-WORKDIR /sass
+ENTRYPOINT [ "/usr/bin/tini", "--" ]
-ENTRYPOINT [ "/sbin/tini", "--", "/usr/local/bin/sass -s ${SASS_STYLE} --watch --poll --stop-on-error sass:css" ]
+CMD /opt/dart-sass/sass -s ${SASS_STYLE} --watch --poll --stop-on-error /sass:/css
 
 # set build timestamp, git and version labels
 ARG INTERNAL_VERSION