feat: add volume-nocopy

[jiwahn]

• Part of Update the list of the unimplemented Docker features (and implement them) #3867

• This patch parses volume-nocopyoption and skip copying the contents from the image to the volume when specified.

• Added unit and integration tests

FROM alpine
RUN mkdir -p /mnt && echo hi > /mnt/initial_file
CMD ["sh"]

╰─$ nerdctl run --rm -it \
  --mount type=volume,source=nocopy-vol,target=/mnt,volume-nocopy \
  nocopy-test \
  sh
/ # ls -la mount
ls: mount: No such file or directory
/ # ls -la /mnt
total 8
drwx------    2 root     root          4096 Aug  7 14:51 .
drwxr-xr-x    1 root     root          4096 Aug  7 14:51 ..
/ # exit

[jiwahn]

+) I thought Adding -v...:nocopy option makes code a little redundant, so I didn't feel like adding it here. But please let me know if it's better to be done in this PR!

[AkihiroSuda]

+) I thought Adding -v...:nocopy option makes code a little redundant, so I didn't feel like adding it here. But please let me know if it's better to be done in this PR!

Does it exist in Docker?
If not no need to implement it

[jiwahn]

Does it exist in Docker?

yes https://github.com/docker/cli/blob/master/man/docker-run.1.md?plain=1#L744C1-L755C14

[AkihiroSuda]

Does it exist in Docker?

yes https://github.com/docker/cli/blob/master/man/docker-run.1.md?plain=1#L744C1-L755C14

Then it should be implemented too

[jiwahn]

Yeah I figured. I will follow up with another pr if that's ok

[Copilot]

Pull request overview

Adds Docker-compatible volume-nocopy support for volume mounts.

Changes:

• Parses and propagates the new mount option.
• Skips initial image-content copying when enabled.
• Adds documentation and unit/integration coverage.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/mountutil/mountutil.go	Stores the no-copy setting.
pkg/mountutil/mountutil_linux.go	Parses and validates the option.
pkg/mountutil/mountutil_linux_test.go	Tests basic parsing.
pkg/cmd/container/run_mount.go	Conditionally skips content copying.
docs/command-reference.md	Documents the option.
cmd/nerdctl/container/container_run_mount_linux_test.go	Tests no-copy behavior end to end.

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