Sets git reference and gitRemoteCommitId.
Jenkins has 2 strategies - 'Merging the pull request with the current target branch revision' and 'The current pull request revision'. When 'Merging the pull request with the current target branch revision' is run, Jenkins creates a local merge commit and runs a job for that particular merge commitId. This commitId is then used for codeql to upload sarif, on upload it throws an error as the merge commit does not exist in github. To resolve this we have introduces a new variable 'gitRemoteCommitId' in commonPipelineEnvironment which gives the remote merge commit id.
