GitHub checkout with environmental variable in Jenkinsfile - jenkins-pipeline

Question

In Jenkins, I have a multibranch pipeline job using a Jenkinsfile. I have disabled the default SCM checkout via:
options {skipDefaultCheckout(true)}
so that I can control the checkout for each stage and use the SSH URL from GitHub. I have a working stage that checks out the "main" branch using:
checkout([
$class: 'GitSCM',
branches: [[name: '*/main']],
extensions: [[$class: 'LocalBranch', localBranch: 'main']],
userRemoteConfigs: [[credentialsId: 'XXX', url: 'git#github.com:XXX.git']]
])
For another stage, I would like to checkout and build/test the branch that is triggered (in this case a feature branch called "feature-0001"). I have tried this (note the change for the branches and extensions lines):
checkout([
$class: 'GitSCM',
branches: [[name: env.BRANCH_NAME]],
extensions: [[$class: 'LocalBranch']],
userRemoteConfigs: [[credentialsId: XXX, url: 'git#github.com:XXX.git']]
])
but I get the following error:
Error when executing failure post condition:
java.io.IOException: Cannot retrieve Git metadata for the build
In addition, the build log also has:
git rev-parse "origin/feature-0001^{commit}" # timeout=10
git rev-parse "feature-0001^{commit}" # timeout=10
I'm not sure where the "^{commit}" comes from or if it's causing any issues.
Any guidance would be appreciated, thank you!
P.S. I have also tried many variations of BRANCH_NAME including
$env.BRANCH_NAME, ${env.BRANCH_NAME}, $BRANCH_NAME, ${BRANCH_NAME}

Answer 1

branches: [[name: "refs/heads/${env.BRANCH_NAME}"]] worked.
I was also using the incorrect url/credentials causing further issues.

Answer 2

If you want an unambiguous way to reference your branch name in the SCM checkout step, try (as explained here):
branches: [[name: 'refs/heads/${env.BRANCH_NAME}']]
The ^{commit} revision specification would therefore apply to the ref refs/heads/${env.BRANCH_NAME}
<rev>^{<type>}, e.g. v0.99.8^{commit}
A suffix ^ followed by an object type name enclosed in brace pair means dereference the object at <rev> recursively until an object of type <type> is found or the object cannot be dereferenced anymore (in which case, barf).
For example, if <rev> is a commit-ish, <rev>^{commit} describes the corresponding commit object.