container: add --health-cmd-mode for CMD healthcheck form

[lohitkolluri]

docker run/create always wraps --health-cmd in CMD-SHELL, which
fails on scratch and other shell-less images (#3719).

Add --health-cmd-mode with two values:

Value	Behavior
shell (default)	wraps command in CMD-SHELL — identical to existing behavior
exec	uses the exec form (CMD), required for images without a shell

This mirrors the CMD / CMD-SHELL distinction in Dockerfile HEALTHCHECK instructions.

Usage

# exec form for scratch / distroless
docker run --health-cmd=/healthcheck --health-cmd-mode=exec my-image

# multi-argument exec form (parsed with shlex)
docker run --health-cmd='/usr/bin/wget -q -O /dev/null http://localhost/' \
           --health-cmd-mode=exec my-image

# explicit shell form — same as omitting --health-cmd-mode
docker run --health-cmd='curl -f http://localhost/' --health-cmd-mode=shell my-image

Test plan

• go test ./cli/command/container/... -run TestParseHealth
• make mddocs (docs regenerated in this commit)

Fixes #3719

[andrebrait]

How about an option --health-cmd-mode with values shell (the default) and exec?

Just in case the future has even more modes possible, so changing this is easier?

[andrebrait]

Or cmd instead of exec, or upper-case, etc.

Up to the maintainers to know what they prefer, but I'm just throwing the idea out there.

[lohitkolluri]

@andrebrait Great suggestion — updated to --health-cmd-mode with string values shell (default, keeps CMD-SHELL behavior) and exec (uses the CMD form). This is cleaner and leaves room for future modes.

Changes in the latest commit:

• --health-cmd-exec bool → --health-cmd-mode string (default "shell")
• Error on unrecognised mode value
• Tests updated for both modes + invalid-mode case
• Docs regenerated via make mddocs

[lohitkolluri]

@thaJeztah — when you have a moment, could you please take a review pass on this? Happy to address any feedback.

Thank you.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[lohitkolluri]

Hi @thaJeztah, just a gentle follow-up whenever you have a moment.

I’ve addressed the lint issues in the latest commit:

• shortened the flag description to resolve the revive line-length warning
• moved the --health-cmd-mode test cases into a separate TestParseHealthCmdMode test to satisfy gocyclo

When convenient, could you please:

1. Approve the workflow runs for this PR, since the forked workflow executions are currently awaiting maintainer approval
2. Set the milestone to 29.5.3 so the validate-milestone check can pass. I don’t have the required permissions to assign milestones in this repository.

Please let me know if there’s anything else you’d like me to update or improve. Thanks again for your time and review. I really appreciate it.