FIX: missing or partial support for pattern substition in variable when cache enabled

[kt315]

Fixes #1246

Description

There is no need to interpolate the variables in the RUN command to calculate the hash because the ARG and ENV variables are added when the CompositeCache is built.
Therefore, we can now use all substitutions from bash.

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes unit tests
• Adds integration tests if needed.

See the contribution guide for more details.

Reviewer Notes

• The code flow looks good.
• Unit tests and or integration tests added.

[kt315]

Dockerfile:

FROM ubuntu:20.04

ARG APP_VERSION=blabla
RUN echo ${APP_VERSION%-*} > test

build

### first time
test_kaniko$ sudo docker run -t --rm -v "$(pwd):/workspace/" gcr.io/kaniko-project/executor --insecure --insecure-pull --use-new-run --cache --cache-run-layers --cache-copy-layers --destination       "10.22.0.52:5000/blabla:test" --build-arg APP_VERSION=blabla2
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Retrieving image ubuntu:20.04 from registry index.docker.io
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Built cross stage deps: map[]
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Executing 0 build triggers
INFO[0000] Building stage 'ubuntu:20.04' [idx: '0', base-idx: '-1']
INFO[0000] Checking for cached layer 10.22.0.52:5000/blabla/cache:8e47b29493a39249c8315644e0c0a393ef91bca5c116643d9dda71268b9c63b1...
INFO[0000] No cached layer found for cmd RUN echo ${APP_VERSION%-*} > test
INFO[0000] Unpacking rootfs as cmd RUN echo ${APP_VERSION%-*} > test requires it.
INFO[0001] ARG APP_VERSION=blabla
INFO[0001] No files changed in this command, skipping snapshotting.
INFO[0001] RUN echo ${APP_VERSION%-*} > test
INFO[0001] Cmd: /bin/sh
INFO[0001] Args: [-c echo ${APP_VERSION%-*} > test]
INFO[0001] Running: [/bin/sh -c echo ${APP_VERSION%-*} > test]
INFO[0001] Taking snapshot of files...
INFO[0001] Pushing layer 10.22.0.52:5000/blabla/cache:8e47b29493a39249c8315644e0c0a393ef91bca5c116643d9dda71268b9c63b1 to cache now
INFO[0001] Pushing image to 10.22.0.52:5000/blabla/cache:8e47b29493a39249c8315644e0c0a393ef91bca5c116643d9dda71268b9c63b1
INFO[0006] Pushed 10.22.0.52:5000/blabla/cache@sha256:1792487d47569fdb19eaaa84227755e2764bee2c86822f2458bb8c34f0fd1a40
INFO[0006] Pushing image to 10.22.0.52:5000/blabla:test
INFO[0011] Pushed 10.22.0.52:5000/blabla@sha256:41df57b887206148d1361f9bc5ade6659cfbb1677b111977d25ebd34230c30c9

### second time
test_kaniko$ sudo docker run -t --rm -v "$(pwd):/workspace/" gcr.io/kaniko-project/executor --insecure --insecure-pull --use-new-run --cache --cache-run-layers --cache-copy-layers --destination       "10.22.0.52:5000/blabla:test" --build-arg APP_VERSION=blabla2
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Retrieving image ubuntu:20.04 from registry index.docker.io
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Built cross stage deps: map[]
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Executing 0 build triggers
INFO[0000] Building stage 'ubuntu:20.04' [idx: '0', base-idx: '-1']
INFO[0000] Checking for cached layer 10.22.0.52:5000/blabla/cache:8e47b29493a39249c8315644e0c0a393ef91bca5c116643d9dda71268b9c63b1...
INFO[0002] Using caching version of cmd: RUN echo ${APP_VERSION%-*} > test
INFO[0002] Skipping unpacking as no commands require it.
INFO[0002] ARG APP_VERSION=blabla
INFO[0002] No files changed in this command, skipping snapshotting.
INFO[0002] RUN echo ${APP_VERSION%-*} > test
INFO[0002] Found cached layer, extracting to filesystem
INFO[0005] Pushing image to 10.22.0.52:5000/blabla:test
INFO[0010] Pushed 10.22.0.52:5000/blabla@sha256:cfc8daa2946f8cc105d0305eb12c7825408db8b8dbedb328065c8fecfc9a920e

without fix

test_kaniko$ sudo docker run -t --rm -v "$(pwd):/workspace/" registry/build_system/kaniko --insecure --insecure-pull --use-new-run --cache --cache-run-layers --cache-copy-layers --destination       "10.22.0.52:5000/blabla:test"
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Retrieving image ubuntu:20.04 from registry index.docker.io
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Built cross stage deps: map[]
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Retrieving image manifest ubuntu:20.04
INFO[0000] Returning cached image manifest
INFO[0000] Executing 0 build triggers
INFO[0000] Building stage 'ubuntu:20.04' [idx: '0', base-idx: '-1']
error building image: error building stage: failed to optimize instructions: failed to process "RUN echo ${APP_VERSION%-*} > test": missing ':' in substitution

[kt315]

@aaron-prindle, hi! Review pls)

[QuanZhang-William]

Changes look good to me. @aaron-prindle, please take a look if you are interested, otherwise we can merge it today

[aaron-prindle]

Thanks for the PR @kt315, LGTM!