[Gradle] Ability to specify absolute path of credential helper

[anuraaga]

Description of the issue:

Currently it is only possible to specify the credential helper suffix (e.g., gcr). This requires an executable docker-credential-gcr to be on the PATH. This manipulation of the PATH may not be ideal, i.e., to allow builds to be reproducible on multiple environments.

Expected behavior:
It is possible to specify the absolute path to a credential helper. I believejib-core already supports passing a java.nio.Path and it just needs to be exposed.

[chanseokoh]

Hi @anuraaga,

Can you elaborate on what your exact use case is? Also, do you want this to be a configurable parameter in pom.xml or build.gradle that you want to check in in a VCS? Or is it OK if you can specify that in a command line? Do you just want to fix a location where docker-credential-gcr is located, or do you also need to be able to specify an arbitrary command name (i.e., not starting with docker-credential prefix)?

[anuraaga]

Hey - my use case is that a Gradle task automatically downloads the gcloud sdk and extracts it into a location under gradle.userHomeDir. This way users don't have to worry about downloading SDKs, etc, the build takes care of everything and a task like :gcloudLoginToCluster can execute the downloaded SDK's gcloud to generate kubeconfig, for example and jib should "just work". But in this case, the gcloud SDK, which includes docker-credential-gcr is not on the system PATH, it is managed by Gradle.

Being able to specify the exact path to the credential helper on a Gradle script would be great. From what I could tell, this might be trivial since this method in core exists that takes a Path.

https://github.com/GoogleContainerTools/jib/blob/master/jib-core/src/main/java/com/google/cloud/tools/jib/frontend/CredentialRetrieverFactory.java#L117

[coollog]

I believe we can allow credHelper to be specified with a path to a credential helper executable (along with the credential helper suffix as we have now). The value specified would first check for existence as a file and then try to be used as a credential helper suffix.

[coollog]

Hi @anuraaga , we've released version 0.10.0 with the ability to set a full path as the credHelper!

[anuraaga]

Thanks! Verified it works great.