[proposal] Emit warning if ADD --chown flag is used with archive file

[simnalamburt]

I noticed a counterintuitive behavior of Moby which is ignoring ADD --chown flag when it is used in conjunction with a compressed file. Moby project had several duplicate issues because of this. It would be better if Moby prohibits such use or displays a warning. What do you think?

I also could not find out where this behavior is documented in the official docs. If this behavior is not documented, it might be better to document it explicitly too.

References

• Add --chown flag to ADD/COPY commands moby#34263 (comment)
• ADD archive file with the --chown flag moby#35525
• uid and gid mismatch when using 'ADD --chown' in Dockerfile moby#36349
• https://docs.docker.com/engine/reference/builder/#add

[dmhursh]

I would like this to at least be a warning. I would prefer it were an error since the results will not match what I believe is the only obviously expect outcome.

Better yet would be to have

ADD --chown user:group tarfile.tar.gz /target/directory

behave like

sudo -u user -g group tar --no-same-owner -C /target/directory xzf tarfile.tar.gz

[thaJeztah]

Let me transfer this ticket to the BuildKit repo, as that's where development is now happening for the builder