docker build hook

docker build on push.md

Build images on tag push

Prepare build machine / remote repo

• Create remote repo (suffix .git is convention for bare repos) git init --bare myrepo.git

• Add docker build hook cp post-receive.bash myrepo/hooks/post-receive

• Make sure docker build runs without any problems

Prepare workstation

• Set up ssh-keys so git can login via ssh (optional)
  ssh-copy-id -i mygitkey user@mygitserver

• Set up alias in ~/.ssh/config for repo server (also optional)

Host myreposerver
         User myuser
         Port 2222
         HostName reposerver.example.com
         IdentityFile mygitkey

• In the git repo, make sure you have a valid Dockerfile

• Add remote (origin or whatever name)
  git remote add origin ssh://myreposerver/path/to/myrepo.git

• Add a tag to a commot you wat to build
  git tag v0.1

• Push tags
  git push origin main --tags

• Build starts

post-receive.bash

#!/bin/bash
# Git hook that builds a container when a new tag is received
# post receive hooks are run at the end so client hangs until build is done
# shellcheck disable=SC2034

cleanup() {
    rm -rf "${builddir}"
}
build_tag() {
    builddir=$(mktemp -d -t XXXX-build)
    trap cleanup EXIT

    repodir=$PWD
    cd "${builddir}" || exit
    umask 0002 # make sure rootless docker can read build context
    git clone -b "${tagname}" "${repodir}" -c advice.detachedHead=false .
    if [[ ! -r Dockerfile ]]; then
        echo "No Dockerfile found."
        exit 0
    fi
    # Build and tag container. Dockerfile should have build-args set
  docker build \
        --build-arg="TAGNAME=${tagname}" \
        --build-arg="AUTHOR=$(git --git-dir "${builddir}"/.git log --format='%an %ae' HEAD^\!)" \
        --build-arg="BUILD_TIME=$(date --iso-8601=minutes)" \
        --build-arg="COMMIT=$(git --git-dir "${builddir}"/.git rev-parse HEAD)" \
        --tag "$(basename "${repodir}")":"${tagname}" \
        --file ./Dockerfile src
}

process_ref() {
    case ${refname} in
        refs/tags/*)
            tagname=${refname##refs/tags/}
            ;;
        refs/heads/*)
            ;;
    esac
}

# Hook input:
# <old-value> SP <new-value> SP <ref-name> LF
while IFS=' ' read -r oldref newref refname; do process_ref "${refname}"; done
# All refs processed
if [[ -z ${tagname} ]]; then
    # no tags to build
    echo no tags to build
    exit 0
fi
# Build last tag (if multiple tags were pushed)
echo "Starting build of tag: ${tagname}"
build_tag "${tagname}"