chore: Revise `Dockerfile`

- Removing bulk of the noise from inline documentation.
- Packages bundled into single line like previous the Alpine version had.
- `CACHE_ZYPPER` is only used as an `ARG` in the `builder` stage.
- `zypper clean` wasn't able to clear anything from the install root, other than the `CACHE_ZYPPER` mount.

Dockerfile

@@ -1,66 +1,35 @@
 # syntax=docker.io/docker/dockerfile:1
-# HereDoc (EOF) feature (avoids needing `&& \`) requires BuildKit:
-# https://docs.docker.com/engine/reference/builder/#here-documents
+
 ARG LEAP_VERSION=15.4
-ARG CACHE_ZYPPER=/tmp/cache/zypper
 ARG INSTALL_ROOT=/rootfs
 
 FROM opensuse/leap:${LEAP_VERSION} as builder
-ARG CACHE_ZYPPER
+ARG CACHE_ZYPPER=/tmp/cache/zypper
 ARG INSTALL_ROOT
 # --mount is only necessary for persisting the zypper cache on the build host,
 # Paired with --cache-dir below, RUN layer invalidation does not clear this cache.
 # Not useful for CI, only local builds that retain the storage.
 RUN --mount=type=cache,target="${CACHE_ZYPPER}",sharing=locked <<EOF
-  INSTALL_DEPS=()
-
-  # Mandatory commands. coreutils required over busybox for date command:
-  # https://github.com/drwetter/testssl.sh/commit/d1f03801738c87b6af39372c45e048af78c73c09
-  INSTALL_DEPS+=(bash procps grep gawk sed coreutils)
-
-  # Support better performance and debugging than hexdump via xxd:
-  # https://github.com/drwetter/testssl.sh/pull/1862
-  # busybox-util-linux (mandatory: hexdump) + busybox-vi (optional: xxd)
-  INSTALL_DEPS+=( busybox-util-linux busybox-vi )
-
-  # Support IDN (Internationalized Domain Names) lookups with drill:
-  # https://github.com/drwetter/testssl.sh/pull/1326
-  INSTALL_DEPS+=( ldns libidn2-0 )
-
-  # Support StartTLS injection:
-  # https://github.com/drwetter/testssl.sh/pull/1810
-  INSTALL_DEPS+=( socat openssl )
-
-  # Support --phone-out checks:
-  # https://github.com/drwetter/testssl.sh/commit/a66f5cfdbcd93427f4408bdd8cfc336488c02bb8
-  INSTALL_DEPS+=( curl )
-
-
   # Provides $VERSION_ID
   source /etc/os-release
-
-  # --releasever required due to no version info in install root.
-  # --installroot installs to location as if it was the system root.
-  # --cache-dir with above `RUN --mount` speeds this step up.
   ZYPPER_OPTIONS=(
     --releasever "${VERSION_ID}"
     --installroot "${INSTALL_ROOT}"
     --cache-dir "${CACHE_ZYPPER}"
   )
 
-  # Sync package repos to get latest updates:
+  # Sync package repos:
   zypper ${ZYPPER_OPTIONS[@]} --gpg-auto-import-keys refresh
 
   zypper ${ZYPPER_OPTIONS[@]} --non-interactive install \
-    --download-in-advance --no-recommends ${INSTALL_DEPS[@]}
+    --download-in-advance --no-recommends \
+    bash procps grep gawk sed coreutils busybox-util-linux busybox-vi ldns libidn2-0 socat openssl curl
 
 
-  # Clears the cache, but this is not stored in the install root location (like DNF does), thus not useful.
-  # zypper ${ZYPPER_OPTIONS[@]} clean --all
-
-  # Unlike DNF, there isn't a `--nodocs` install option, manually remove some excess weight (9 MiB):
+  ## Cleanup (reclaim approx 13 MiB):
+  # None of this content should be relevant to the container:
   rm -r "${INSTALL_ROOT}/usr/share/"{licenses,man,locale,doc,help,info}
-  # Neither of these should be needed in the container, removes 4MiB
+  # Functionality that the container doesn't need:
   rm "${INSTALL_ROOT}/usr/share/misc/termcap"
   rm -r "${INSTALL_ROOT}/usr/lib/sysimage/rpm"
 EOF