more efficient docker build

Dockerfile

@@ -1,10 +1,20 @@
 ARG PHP_VERSION=8.2
 
+# Install base packages which all stages (build, test, run) need
+FROM debian:bookworm AS base
+RUN apt update && apt upgrade -y && apt install -y \
+    php${PHP_VERSION}-cli php${PHP_VERSION}-gd php${PHP_VERSION}-zip php${PHP_VERSION}-xml php${PHP_VERSION}-mbstring \
+    php${PHP_VERSION}-pgsql php${PHP_VERSION}-mysql php${PHP_VERSION}-sqlite3 \
+    gosu curl imagemagick ffmpeg zip unzip && \
+    rm -rf /var/lib/apt/lists/*
+
+# Composer has 100MB of dependencies, and we only need that during build and test
+FROM base AS composer
+RUN apt update && apt upgrade -y && apt install -y composer php${PHP_VERSION}-xdebug && rm -rf /var/lib/apt/lists/*
+
 # "Build" shimmie (composer install - done in its own stage so that we don't
 # need to include all the composer fluff in the final image)
-FROM debian:bookworm AS app
+FROM composer AS app
-RUN apt update && apt upgrade -y
-RUN apt install -y composer php${PHP_VERSION}-gd php${PHP_VERSION}-xml php${PHP_VERSION}-sqlite3 php${PHP_VERSION}-xdebug imagemagick
 COPY composer.json composer.lock /app/
 WORKDIR /app
 RUN composer install --no-dev
@@ -13,9 +23,7 @@ COPY . /app/
 # Tests in their own image. Really we should inherit from app and then
 # `composer install` phpunit on top of that; but for some reason
 # `composer install --no-dev && composer install` doesn't install dev
-FROM debian:bookworm AS tests
+FROM composer AS tests
-RUN apt update && apt upgrade -y
-RUN apt install -y composer php${PHP_VERSION}-gd php${PHP_VERSION}-xml php${PHP_VERSION}-sqlite3 php${PHP_VERSION}-xdebug imagemagick
 COPY composer.json composer.lock /app/
 WORKDIR /app
 RUN composer install
@@ -25,32 +33,17 @@ RUN [ $RUN_TESTS = false ] || (\
     echo '=== Installing ===' && mkdir -p data/config && INSTALL_DSN="sqlite:data/shimmie.sqlite" php index.php && \
     echo '=== Smoke Test ===' && php index.php get-page /post/list && \
     echo '=== Unit Tests ===' && ./vendor/bin/phpunit --configuration tests/phpunit.xml && \
-    echo '=== Coverage ===' && ./vendor/bin/phpunit --configuration tests/phpunit.xml --coverage-text && \
+    echo '=== Coverage ===' && XDEBUG_MODE=coverage ./vendor/bin/phpunit --configuration tests/phpunit.xml --coverage-text && \
     echo '=== Cleaning ===' && rm -rf data)
 
-# Build su-exec so that our final image can be nicer
-FROM debian:bookworm AS suexec
-RUN apt update && apt upgrade -y
-RUN apt install -y --no-install-recommends gcc libc-dev curl
-RUN curl -k -o /usr/local/bin/su-exec.c https://raw.githubusercontent.com/ncopa/su-exec/master/su-exec.c; \
-    gcc -Wall /usr/local/bin/su-exec.c -o/usr/local/bin/su-exec; \
-    chown root:root /usr/local/bin/su-exec; \
-    chmod 0755 /usr/local/bin/su-exec;
-
 # Actually run shimmie
-FROM debian:bookworm
+FROM base
 EXPOSE 8000
 HEALTHCHECK --interval=1m --timeout=3s CMD curl --fail http://127.0.0.1:8000/ || exit 1
 ENV UID=1000 \
     GID=1000 \
     UPLOAD_MAX_FILESIZE=50M
-RUN apt update && apt upgrade -y && apt install -y \
-    php${PHP_VERSION}-cli php${PHP_VERSION}-gd php${PHP_VERSION}-zip php${PHP_VERSION}-xml php${PHP_VERSION}-mbstring \
-    php${PHP_VERSION}-pgsql php${PHP_VERSION}-mysql php${PHP_VERSION}-sqlite3 \
-    curl imagemagick ffmpeg zip unzip && \
-    rm -rf /var/lib/apt/lists/*
 COPY --from=app /app /app
-COPY --from=suexec /usr/local/bin/su-exec /usr/local/bin/su-exec
 
 WORKDIR /app
 CMD ["/bin/sh", "/app/tests/docker-init.sh"]

tests/docker-init.sh

@@ -4,7 +4,7 @@ useradd -ms /bin/bash -u $UID -g $GID shimmie
 mkdir -p /app/data
 chown $UID:$GID /app/data
 export PHP_CLI_SERVER_WORKERS=8
-exec /usr/local/bin/su-exec shimmie:shimmie \
+exec gosu shimmie:shimmie \
   /usr/bin/php \
     -d upload_max_filesize=$UPLOAD_MAX_FILESIZE \
     -d post_max_size=$UPLOAD_MAX_FILESIZE \