feat: remove smart cache system in zsh

zsh/Dockerfile

@@ -1,24 +1,5 @@
-# This Dockerfile image is optimized to maximize Docker layer cache usage among
-# the builds of the different image tags. Since the different tags of the image
-# are built at the same time, we can cache the dependency-installation step
-# and then copy the zsh image (the thing that changes between tags) on top of it.
-#
-# Idea taken from: https://stackoverflow.com/a/48545669/5798232.
-#
-# Step 1: reference the parent image in a pre-build step.
-# Step 2: copy the parent image filesystem on top of our new image, *after*
-# dependencies have been installed.
-
-## PRE-BUILD STEP
 ARG ZSH_VERSION=latest
-FROM zshusers/zsh:${ZSH_VERSION} as zsh
-
-
-## MAIN IMAGE BUILD
-
-# IMPORTANT: this is the image that zshusers/zsh is based on. We need to use
-# the same for compatibility so that there are no conflicts in the COPY step.
-FROM bitnami/minideb:buster
+FROM zshusers/zsh:${ZSH_VERSION}
 
 # image metadata
 LABEL org.opencontainers.image.title="ohmyzsh/zsh"
@@ -37,8 +18,5 @@ RUN install_packages \
       git \
       curl
 
-# this is the point where we copy Zsh from the parent image
-COPY --from=zsh / /
-
 # install ohmyzsh
 RUN sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)" "" --unattended