Dockerfile example of emacs installation

# The emacs installation phase itself takes aroun 7 minutes to complete
# for the first time after we change something in the initial or second
# stage - everything under them will have to be rerun... meaning another
# 7 minutes of your life. Not cool.

# so what I found is that you can split the Dockerfile into stages. I
# will put the steps that might change frequently towards the end of
# the Dockerfile to maximize caching. By separating the stages in this
# manner, Docker will reuse the intermediate images created in each
# stage, utilizing the cache for the unchanged layers. When changes
# occur, only the steps AFTER THE MODIFICATION will be re-executed.

# -----------------------------------------------------------
# INITIAL STAGE: Installing essential packages and tools
FROM ubuntu:latest AS base

RUN apt update && apt upgrade -y \
    && apt install sudo make wget -y

# -----------------------------------------------------------
# SECOND STAGE: Installing Git and cloning the repository
FROM base AS gitclone

RUN apt-get install -y git \
    && git clone https://github.com/arvydasg/dotfiles.git /root/dotfiles

# -----------------------------------------------------------
# THIRD STAGE: Emacs installation
FROM gitclone AS emacs

WORKDIR /root
COPY compile-install-emacs.sh compile-install-emacs.sh
RUN chmod +x compile-install-emacs.sh
RUN sh compile-install-emacs.sh

# -----------------------------------------------------------
# FOURTH STAGE: Random stuff
# since emacs has been installed(heaviest process), we can do any
# random installs and actions here now, so only the steps under would
# be rerun and not the whole container including the emacs compilation
# stage(Third stage)
RUN apt install vim htop tmux -y

# -----------------------------------------------------------
# FINAL STAGE
FROM emacs AS final

ENTRYPOINT ["emacs"]