Dynamically Fill Jenkins Choice Parameter With Git Branches In a Specified Repo

Question

I have a parameterized Jenkins job which requires the input of a specific Git branch in a specific Git repo. Currently this parameter is a string parameter.

Is ther

Answer 1

I'm aware to the fact that in the original question Jenkins pipeline was not mentioned, but if it is still applicable (using it), I find this solution easy to maintain and convenient.

This approach describe the settings required to compose a Jenkins pipeline that "polls" (list) dynamically all branches of a particular repository, which then lets the user run the pipeline with some specific branch when running a build of this job.

The assumptions here are:

• The Jenkins server is 2.204.2 (hosted on Ubuntu 18.04)
• The repository is hosted in a BitBucket.

First thing to do is to provide Jenkins credentials to connect (and "fetch") to the private repository in BitBucket. This can be done by creating an SSH key pair to "link" between the Jenkins (!!) user on the machine that hosts the Jenkins server and the (private) BitBucket repository.

1. First thing is to create an SSH key to the Jenkins user (which is the user that runs the Jenkins server - it is most likely created by default upon the installation):

   guya@ubuntu_jenkins:~$ sudo su jenkins 
   [sudo] password for guya:
   jenkins@ubuntu_jenkins:/home/guya$ ssh-keygen
   

   The output should look similar to the following:

Generating public/private rsa key pair. Enter file in which to save the key
(/var/lib/jenkins/.ssh/id_rsa): Created directory '/var/lib/jenkins/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /var/lib/jenkins/.ssh/id_rsa. Your public key has been saved in /var/lib/jenkins/.ssh/id_rsa.pub. The key fingerprint is: SHA256:q6PfEthg+74QFwO+esLbOtKbwLG1dhtMLfxIVSN8fQY jenkins@ubuntu_jenkins The key's randomart image is: +---[RSA 2048]----+ | . .. o.E. | | . . .o... o | | . o.. o | | +.oo | | . ooX..S | |..+.Bo* . | |.++oo* o. | |..+*..*o | | .=+o==+. | +----[SHA256]-----+ jenkins@ubuntu_jenkins:/home/guya$

2. Now the content of this SSH key needs to be set in the BitBucket repository as follows:

• Create (add) an SSH key in the BitBucket repository by going to: Settings --> Access keys --> Add key.
• Give the key Read permissions and copy the content of the PUBLIC key to the "body" of the key. The content of the key can be displayed by running: cat /var/lib/jenkins/.ssh/id_rsa.pub

3. After that the SSH key was set in the BitBucket repository, we need to "tell" Jenkins to actually USE it when it tries to fetch (read in this case) the content of the repository. NOTE that by letting Jenkins know, actually means let user jenkins this "privilege".

This can be done by adding a new  SSH User name with private key to the Jenkins --> Credentials --> System --> Global Credentials --> Add credentials.

• In the ID section put any descriptive name to the key.
• In the Username section put the user name of the Jenkins server which is jenkins.
• Tick the Private key section and paste the content of the PRIVATE key that was generated earlier by copy-paste the content of: ~/.ssh/id_rsa. This is the private key which start with the string:-----BEGIN RSA PRIVATE KEY----- and ends with the string: -----END RSA PRIVATE KEY-----. Note that this entire "block" should be copied-paste into the above section.

4. Install the Git Parameter plugin that can be found in its official page here

5. The very minimum pipeline that is required to list (dynamically) all the branches of a given repository is as follows:

   pipeline 
   { 
       agent any parameters
       { 
           gitParameter branchFilter: 'origin/(.*)', defaultValue: 'master', name: 'BRANCH', type: 'PT_BRANCH' 
       }
       stages 
       { 
          stage("list all branches") 
          { 
              steps 
              { 
                   git branch: "${params.BRANCH}", credentialsId: "SSH_user_name_with_private_key", url: "ssh://git@myCompanyBitBucketSite.com:port/myRepository.git" 
              } 
         } 
      } 
   }
   

NOTES:

• The defaultValue is set to master so that if no branches exist - it will be displayed in the "drop list" of the pipeline.
• The credentialsId has the name of the credentials configured earlier.
• In this case I used the SSH URL of the repository in the url parameter.
• This answer assumes (and configured) that the git server is BitBucket. I assume that all the "administrative" settings done in the initial steps, have their equivalent settings in GitHub.