Jenkins Workflow Checkout Accessing BRANCH_NAME and GIT_COMMIT - jenkins

Question

I cannot seem to extract $GIT_COMMIT and $BRANCH_NAME from a Jenkins Workflow Checkout step.
I would like to be able to send this information through to my Gradle scripts in order to pass it onto external sources such as Static analysis etc.
Currently I try to run this:
checkout([$class: 'GitSCM', branches: [[name: '*/master']], userRemoteConfigs: [[credentialsId: '2b74a351-67d5-4d00-abd3-49842a984201', url: 'ssh://git#corporate.com:repo.git']]])
And I would like to achieve the following or something similar:
// Specified variables that can be reused
def branch = ${BRANCH_NAME}
def commit = ${GIT_COMMIT}
Or maybe this would work too:
print "BRANCH: ${BRANCH_NAME}, COMMIT: ${GIT_COMMIT}"
// or the following
print "BRANCH: ${env.BRANCH_NAME}, COMMIT: ${env.GIT_COMMIT}"
I did find the following issue which seems to be resolved but it doesn't work in version 1.15:
https://issues.jenkins-ci.org/browse/JENKINS-30252
Anyone have any ideas how to workaround this or if there's a variable I cannot find?

Answer 1

First of all,
def branch = ${BRANCH_NAME}
is not valid Groovy, or at least not doing what you think. Perhaps you meant
def branch = "${BRANCH_NAME}"
which would just be a silly way of writing
def branch = BRANCH_NAME
Anyway environment variables are not currently accessible directly as Groovy variables in Pipeline (there is a proposal to allow it); you need to use the env global variable:
def branch = env.BRANCH_NAME
From within an external process, such as a sh step, it is an actual environment variable, so
sh 'echo $BRANCH_NAME'
works (note that ' means Groovy is not interpolating the variable).
Now, JENKINS-30252 was referring to multibranch projects. If you created a standalone Pipeline job, this variable will not be set.
Anyway in your case your checkout step is always checking out the master branch. If you actually have a multibranch project, then your Jenkinsfile should be using
checkout scm
which will check out a commit on the correct branch (always matching the revision of Jenkinsfile itself).
As to the commit hash, pending JENKINS-26100 this is not available automatically, but you can use something like
sh 'git rev-parse HEAD > commit'
def commit = readFile('commit').trim()
to access it.

Answer 2

I have two Jenkins instances.
In both instances, GIT_COMMIT and BRANCH_NAME environment variables are not defined.
When I try to get them from the return value of checkout() call, each instance behaves differently.
Jenkins Instance 1
Jenkins version: 2.46.1
"Pipeline: SCM Step" plugin version: 2.5
Trying to access the environment variable as explained in the checkout documentation fails.
def scmVars = checkout([$class: 'GitSCM', branches: [[name: '*/master']],
userRemoteConfigs: [[credentialsId: '2b74a351-67d5-4d00-abd3-
49842a984201', url: 'ssh://git#corporate.com:repo.git']]])
def commitHash = scmVars.GIT_COMMIT
scmVars returns NULL, and accessing scmVars.GIT_BRANCH fails with exception java.lang.NullPointerException: Cannot get property 'GIT_BRANCH' on null object.
So I had to do the following in order to get the branch:
sh 'git name-rev --name-only HEAD > GIT_BRANCH'
sh 'cat GIT_BRANCH'
git_branch = readFile('GIT_BRANCH').trim()
env.GIT_BRANCH = git_branch
Jenkins Instance 2
Jenkins version: 2.60.2
"Pipeline: SCM Step" plugin version: 2.6
In this instance, I could do the following with success:
def scmVars = checkout([$class: 'GitSCM', branches: [[name: '*/master']],
userRemoteConfigs: [[credentialsId: '2b74a351-67d5-4d00-abd3-
49842a984201', url: 'ssh://git#corporate.com:repo.git']]])
env.GIT_COMMIT = scmVars.GIT_COMMIT
env.GIT_BRANCH = scmVars.GIT_BRANCH
So please check which approach works for your Jenkins instance and use it.

Answer 3

If you want to access the BRANCH_NAME from Jenkins environment variable as a shell script, use the below snippet.
sh 'echo Branch Name: $BRANCH_NAME'
The response should be as below:
Branch Name: the_checkedout_branch