Adapt mattermost plugins to build ARM executables

mm-plugin-mod-arm

#!/usr/bin/env bash

# vim: ft=sh

set -o errexit

cmds=('diff' 'go' 'jq (github.com/stedolan/jq)' 'patch')

for cmd in "${cmds[@]}"; do
    command -v "${cmd%% *}" >/dev/null 2>&1 \
        || { echo "$0: $cmd must be installed" >&2; exit 1; }
done

case $1 in
    arm|armv7|armv7l) ARCH=arm;;
    arm64|aarch64) ARCH=arm64;;
    *) ARCH="$(go env GOARCH)";;
esac

DIR="$(pwd)"
PLUGIN_ID="$(jq -r '.id' < "$DIR/plugin.json")"

declare -a changelog
changelog=('# Changelog:')

if [[ -s "$DIR/Makefile" ]]; then
    # Find the server build command and modify it to target linux ARM.
    GO_BUILD=$(sed -n \
        "/env GOOS=linux GOARCH=amd64 \$(GO) build/ { s/amd64/$ARCH/gp;q; }" \
        "$DIR/Makefile")

    # Uncomment if it was commented out.
    GO_BUILD="${GO_BUILD#*\#}"

    # Comment out all existing build commands and insert the 'new' one.
    # A backup of the unmodified Makefile is saved as Makefile.orig
    RE='[[:alnum:]]\{1,20\}'
    sed -i.orig \
        -e "/env GOOS=$RE GOARCH=$RE \$(GO) build/ s/^[^#]/#&/" \
        -e $'/\$(GO) build \$(GO_BUILD_FLAGS) -o dist\/plugin-linux-amd64/ i\\\n'"${GO_BUILD}"$'\n' \
        "$DIR/Makefile"

    dist="$(echo "${GO_BUILD##*-o }" | sed 's/;$//')"
    changelog+=('Makefile:')
    changelog+=("	changed \`go build\` to build: $dist")
else
    echo "$0: skipping Makefile: file not found" >&2
fi

if [[ -s "$DIR/plugin.json" ]]; then
    # Replace the path to the server executable with the new path.
    fn="setpath([\"server\"]; {\"executable\": \"server/dist/plugin-linux-$ARCH\"})"
    json=$(jq --indent 4 "$fn" < "$DIR/plugin.json")
    # A backup of the unmodified plugin.json is saved as plugin.json.orig
    diff -ub "$DIR/plugin.json" <(echo "$json") | patch -bs

    path="$(jq -c '.server' < "$DIR/plugin.json")"
    changelog+=('plugin.json:')
    changelog+=("	modified path: \"server\": $path")
else
    echo "$0: skipping plugin.json: file not found" >&2
fi

if (( ${#changelog[@]} > 1 )); then
    printf '%s\n' "${changelog[@]}"
    echo
    echo '# To build and install the plugin:'
    echo "cd $DIR && make dist"
    echo "sudo chown mattermost:mattermost dist/$PLUGIN_ID-*.tar.gz"
    echo "mmctl plugin delete $PLUGIN_ID # if already installed"
    echo "mmctl plugin add $DIR/dist/$PLUGIN_ID-*.tar.gz"
    echo "mmctl plugin enable $PLUGIN_ID"
fi

# NOTE
# If `go build` complains about broken dependencies, make sure, the plugin uses a module
# aware version of mattermost-server
# cf. https://github.com/mattermost/mattermost-plugin-starter-template/blob/master/go.mod

# Installing with plain mattermost command (without mmctl):
# cd /opt/mattermost
# sudo -u mattermost ./bin/mattermost plugin delete $PLUGIN_ID
# sudo -u mattermost ./bin/mattermost plugin add $DIR/dist/$PLUGIN_ID-*.tar.gz
# sudo -u mattermost ./bin/mattermost plugin enable $PLUGIN_ID