Instructions with comments embedded in its keyword are incorrectly parsed and flagged as errors

[rcjsuen]

FROM alpine
FR\
#
OM alpine
HE\
#
AL\
#
THCHECK NONE

$ docker build .
Sending build context to Docker daemon     47MB
Step 1/3 : FROM alpine
latest: Pulling from library/alpine
a0d0a0d46f8b: Pull complete 
Digest: sha256:e1c082e3d3c45cccac829840a25941e679c25d438cc8412c2fa221cf1a824e6a
Status: Downloaded newer image for alpine:latest
 ---> 14119a10abf4
Step 2/3 : FROM alpine
 ---> 14119a10abf4
Step 3/3 : HEALTHCHECK NONE
 ---> Running in 199aef9f80c3
Removing intermediate container 199aef9f80c3
 ---> 6af4b03eec25
Successfully built 6af4b03eec25

$ node bin/dockerfile-utils lint
Line: 2-3
FR\
^^^
#
^
Error: Unknown instruction: FR#

Line: 4
OM alpine
^^
Error: Unknown instruction: OM

Line: 5-6
HE\
^^^
#
^
Error: Unknown instruction: HE#

Line: 7-8
AL\
^^^
#
^
Error: Unknown instruction: AL#

Line: 9
THCHECK NONE
^^^^^^^
Error: Unknown instruction: THCHECK