semver-docker-build.sh

#!/bin/bash

# This script build docker images and create docker tags using git tags with Semantic Versioning pattern
# https://semver.org/spec/v2.0.0.html
# However, it only partially supports pre-release tags as mentioned in part 9 (https://semver.org/spec/v2.0.0.html#spec-item-9)
# Supported git tags: v1.0.0, v1.0.0-beta.1, v1.0.0-alpha.1

# Array of repos for the docker image
REPOS=("<REPO_URL_1>" "<REPO_URL_2>")
SEMANTIC_VERSION_PATTERN="^v([0-9]+)\.([0-9]+)\.([0-9]+)(-([A-Za-z-]+(\.[0-9A-Za-z-]+)?))?$"

usage() {
    echo "Usage: $0 [options...]" 1>&2
    echo "-f  Forces clean build, if HEAD is ahead of git tag" 1>&2
    echo "-r  Pushs the docker images" 1>&2
    echo "-t  Test run, only prints docker image tags" 1>&2
    exit 1
}

while getopts ":frt" o; do
    case "${o}" in
    f)
        FORCE="true"
        ;;
    r)
        RELEASE="true"
        ;;
    t)
        DRY_RUN="true"
        ;;
    *)
		usage
		;;
    esac
done
shift $((OPTIND - 1))

if [ "$1" = "--help" ] || [ "$1" = "-h" ]; then
    usage
fi

# get the last tag which matches the semantic versioning pattern
VERSION_TAG=$(git describe --tags --abbrev=0 --match "v*.*.*" 2>/dev/null)

# if it is a gitlab job, it uses the CI_COMMIT_TAG
if [[ "$CI_COMMIT_TAG" =~ $SEMANTIC_VERSION_PATTERN ]]; then
    echo "Build from CI_COMMIT_TAG: $CI_COMMIT_TAG"
    VERSION_TAG="$CI_COMMIT_TAG"
fi

if [ -z "$VERSION_TAG" ]; then
    echo "Keine Git-Versions-Tags vorhanden" 1>&2
    exit 1
fi

# If there are changes in the tree and/or the version tag is behind the HEAD, the build is "dirty".
# However, a nigthly tag is ALWAYS created
GIT_REVISION=$(git rev-parse --short HEAD)
SUFFIX=""
if [ -n "$(git status --porcelain)" ]; then
    echo "Dirty build..."
    SUFFIX="-dirty"
fi

# If HEAD is ahead of the version tag, we also have a dirty build
if [ "$(git rev-list -n 1 $VERSION_TAG)" != "$(git rev-parse HEAD)" ] && [ "$SUFFIX" = "" ]; then
    echo "Dirty build..."
    SUFFIX="-dirty"
fi

# remove the suffix if we force a clean build
if [[ "$FORCE" == "true" ]]; then SUFFIX=""; fi

# Extract Major Minor, Patch and Pre-release
MAJOR=""
MINOR=""
PATCH=""
PRE_RELEASE=""
if [[ $VERSION_TAG =~ $SEMANTIC_VERSION_PATTERN ]]; then
    MAJOR="${BASH_REMATCH[1]}"
    MINOR="${BASH_REMATCH[2]}"
    PATCH="${BASH_REMATCH[3]}"
    PRE_RELEASE="${BASH_REMATCH[5]}"
    test -n "$PRE_RELEASE" && PRE_RELEASE="-${PRE_RELEASE}"
else
    echo "invalid Semantic Versioning Tag (source: https://semver.org/spec/v2.0.0.html)"
    exit 1
fi

VERSION="${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}"

if [[ "$DRY_RUN" == "true" ]]; then
    echo "=== Images ==="
    for IMAGE_TAG in ${REPOS[@]}; do
        echo
        echo "$IMAGE_TAG:nightly"
        test -z "$PRE_RELEASE" && echo "$IMAGE_TAG:latest${SUFFIX}"
        echo "$IMAGE_TAG:${MAJOR}${PRE_RELEASE}${SUFFIX}"
        echo "$IMAGE_TAG:${MAJOR}.${MINOR}${PRE_RELEASE}${SUFFIX}"
        echo "$IMAGE_TAG:${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}"
        echo "$IMAGE_TAG:${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}-${GIT_REVISION}"
        echo
    done
    exit 0
fi

# build the --tag args for the build command
TAGS=
for IMAGE in ${REPOS[@]}; do
    TAGS+=" --tag $IMAGE:nightly"
    test -z "$PRE_RELEASE" && TAGS+=" --tag $IMAGE:latest${SUFFIX}" # only latest if we haven't a pre-release
    TAGS+=" --tag $IMAGE:${MAJOR}${PRE_RELEASE}${SUFFIX}"
    TAGS+=" --tag $IMAGE:${MAJOR}.${MINOR}${PRE_RELEASE}${SUFFIX}"
    TAGS+=" --tag $IMAGE:${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}"
    TAGS+=" --tag $IMAGE:${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}-${GIT_REVISION}"
done

docker build $TAGS \
    --build-arg VERSION="$VERSION" \
    --build-arg GIT_REVISION="$GIT_REVISION" \
    --build-arg DATE="$(date +%Y-%m-%dT%H:%M:%S%z)" .

if [[ $? == 0 ]] && [[ "$RELEASE" == "true" ]]; then
    for IMAGE_TAG in ${REPOS[@]}; do
        docker push "$IMAGE_TAG:nightly"
        test -z "$PRE_RELEASE" && docker push "$IMAGE_TAG:latest${SUFFIX}" # only latest if we haven't a pre-release
        docker push "$IMAGE_TAG:${MAJOR}${PRE_RELEASE}${SUFFIX}"
        docker push "$IMAGE_TAG:${MAJOR}.${MINOR}${PRE_RELEASE}${SUFFIX}"
        docker push "$IMAGE_TAG:${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}"
        docker push "$IMAGE_TAG:${MAJOR}.${MINOR}.${PATCH}${PRE_RELEASE}${SUFFIX}-${GIT_REVISION}"
    done
fi