MAINTAINER to LABEL conversion does not escape embedded quotes #70

Rewriting MAINTAINER into LABEL org.opencontainers.image.authors="..." wraps the value in double quotes without escaping the quotes it already contains.

Reproduce

FROM alpine
MAINTAINER Jane Doe "jane@example.com"

dockerfmt Dockerfile

Actual

FROM alpine
LABEL org.opencontainers.image.authors="Jane Doe "jane@example.com"

The quotes no longer pair up, and docker build fails on the output:

failed to process "\"Jane Doe \"jane@example.com\"": unexpected end of statement while looking for matching double-quote

Expected

Escape embedded quotes:

LABEL org.opencontainers.image.authors="Jane Doe \"jane@example.com\""

Leaving MAINTAINER unchanged when the value contains a quote would also work.

Impact

With --write the Dockerfile no longer builds. One of the three MAINTAINER lines in a sample of about 450 real-world Dockerfiles had quotes in its value.

Reproduced with v0.5.4 and with main at a5868c2.