fix: do not panic on an invalid image name regexp

[arpitjain099]

Hi, I ran into a crash while working with an images override and traced it back to IsImageMatched in the api module.

The image name that comes from a kustomization's images[].name is interpolated straight into a regexp, and the compile error was discarded:

pattern, _ := regexp.Compile("^" + t + "(:[a-zA-Z0-9_.{}-]*)?...")
return pattern.MatchString(s)

If the name isn't a valid regexp (for example [), regexp.Compile returns (nil, err) and the following pattern.MatchString dereferences the nil *Regexp, so kustomize build panics with a SIGSEGV instead of failing cleanly. This is reachable in practice: a name like that in a remote base that you don't control (a common GitOps setup) takes down the whole build.

The fix keeps the exact same regex string and just checks the error, returning false when the name can't compile. That preserves the existing semantics, since a name that matches nothing leaves the image untouched, which is the same outcome you already get for any name that doesn't match a container.

Verification:

• go test ./internal/image/ ./filters/imagetag/ passes.
• Added a unit test in internal/image with the name [.
• Added a krusty end-to-end case (a kustomization with images: [{name: "[", newTag: v2}] over a Deployment) that panics on master and builds through cleanly with this change.

Thanks for taking a look.

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[koba1t]

/ok-to-test

[koba1t]

@arpitjain099
Thank you for your contribution!
I think this is a bug that we need to be fixed.

/lgtm
/approve

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: arpitjain099, koba1t

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