Add option to source env from file

README.md

@@ -86,6 +86,7 @@ docker run --rm --user=$(id -u) --volume=$HOME:$HOME:ro --workdir=$PWD --env=PLU
 | `annotation`        | PLUGIN_ANNOTATION        | `none`           | Annotations (also known as labels) to add to image                                              |
 | `push`              | PLUGIN_PUSH              | `true`           | Push images if output names are set.                                                            |
 | `auth`              | PLUGIN_AUTH              | `none`           | Auth for private registries                                                                     |
+| `env-file`          | PLUGIN_ENV_FILE          | `none`           | Source environment values from given file                                                       |
 
 ## Alternatives
 

entrypoint.sh

@@ -5,6 +5,15 @@ set -eu;
 ## check input
 ##
 
+if [[ -n "${PLUGIN_ENV_FILE:-}" ]]; then
+	if [[ ! -f "PLUGIN_ENV_FILE" ]]; then
+		echo "Env file $PLUGIN_ENV_FILE not found."
+		exit 1
+	fi
+	# shellcheck source=/dev/null
+	source "$PLUGIN_ENV_FILE"
+fi
+
 BUILDCTL_CONTEXT=${PLUGIN_CONTEXT:-$(pwd)}
 BUILDCTL_DOCKERFILE=$(dirname "${PLUGIN_DOCKERFILE:-$BUILDCTL_CONTEXT/Dockerfile}")
 if [[ ! -f $BUILDCTL_DOCKERFILE/Dockerfile ]]; then