docker-multiphase-handler

Enables proper handling of multiphase dockerfiles

Usage

Using the following dockerfile as an example:

FROM ubuntu AS named-stage

RUN some-command

# stage unnamed
FROM ubuntu

RUN another-command

FROM alpine AS built-app

Valid flags:

• --file | -f: Name of the Dockerfile (Default is PATH/Dockerfile)
• --prefix | -p: Prefix for unnamed stages (Default is unnamed-)
• --output-path | -o: Path to output rewritten dockerfile (Default is stdout)

List Stages

Lists all stages in a dockerfile. If the stage is unnamed, then a temporary stage name is output.

docker-multiphase-handler list-stages

named-stage
unnamed-1
built-app

Check if Dockerfile needs rewrite

Exit 0 if the specified Dockerfile does not need to be rewritten, exits 1 if it does need to be rewritten

docker-multiphase-handler needs-rewrite

Rewrite Dockerfile

Rewrites the specified Dockerfile to ensure each stage is named. May reformat dockerfile and remove comments.

docker-multiphase-handler rewrite

Outputs the following to stdout.

FROM ubuntu AS named-stage

RUN some-command

FROM ubuntu AS unnamed-1

RUN another-command

FROM alpine AS built-app

The flag --output-path can be specified to specify a path to write it to.