I added a few comments to https://github.com/jenkinsci/atlassian-bitbucket-server-integration-plugin/pull/192.

Hi! there is some issues with giflow like branch naming in multibranch pipeline
In build link View Branch:

branch name:

feature/DEVOPS-128

url tail:
/commits?sourceBranch=refs%2Fheads%2Ffeature*%252F*DEVOPS-128
%252 - is double slash, so BB  can't find source branch to compare

sam117, the bug seems to be that the externalLinkUtils.createBranchDiffLink(scmRepository, target.getName()) calls in BitbucketJobLinkActionFactory use the job name rather than the branch name. That code was last changed in 2021-05-17 for this JENKINS-63070.

For the "Multibranch Pipeline Job built with the SCM Source" case, I think this could use SCMHead.HeadByItem.findHead(Item item) and then SCMHead.getName(). Perhaps there is an alternative approach via branch-api-plugin, as well.

For the "Multibranch Pipeline Job built with an SCMStep" case, I am not sure how this should be done.

https://github.com/jenkinsci/atlassian-bitbucket-server-integration-plugin/blob/bce76f1f76daff3fb587ca94cb0c2208b8afc71e/src/main/java/com/atlassian/bitbucket/jenkins/internal/link/BitbucketExternalLinkUtils.java#L44

maybe branch.toString()
or use java.net.URLDecoder  may be helpful?

The "Multibranch Pipeline Job built with an SCMStep" case apparently refers to com.atlassian.bitbucket.jenkins.internal.scm.BitbucketSCMStep ("bbs_checkout" in pipeline; source) or org.jenkinsci.plugins.workflow.steps.scm.GenericSCMStep ("checkout" in pipeline; source), which extend org.jenkinsci.plugins.workflow.steps.scm.SCMStep (source). (jenkins.plugins.git.GitStep ("git" in pipeline; source) likewise extends it, but it is a final class and its createSCM() method creates an instance of GitSCM, which would not pass the scm instanceof BitbucketSCM check.)

I think it should somehow use the branches that were checked out by those steps, but it is not clear to me how to do this because BitbucketSCM.branches lists branch specs rather than branches, and they can have wildcards in them.

https://github.com/jenkinsci/atlassian-bitbucket-server-integration-plugin/blob/bce76f1f76daff3fb587ca94cb0c2208b8afc71e/src/main/java/com/atlassian/bitbucket/jenkins/internal/link/BitbucketExternalLinkUtils.java#L44

Well, the parameter of BitbucketExternalLinkUtils.createBranchDiffLink is String branch rather than String job, so I think this should be kept as is and the caller should be changed.

maybe +branch.toString()

Would have no effect because it's already a String.

or use +java.net.URLDecoder may be helpful?

If you were going to explicitly decode the job name to a branch name, then that should be done using jenkins.branch.NameEncoder, for consistency with MultiBranchProject.getItemByBranchName. However, because BitbucketJobLinkActionFactory gets the repository information from the BitbucketSCM and BitbucketSCMSource instances, it should get the branch names from those as well, instead of assuming that the branch names have anything to do with the job name.

Related code in the Bitbucket Branch Source plugin: https://github.com/jenkinsci/bitbucket-branch-source-plugin/blob/c79f7c340cac7455b90d963bdaba9f4fb7dd2c25/src/main/java/com/cloudbees/jenkins/plugins/bitbucket/BitbucketSCMSource.java#L1051-L1076

It just operates based on the SCMHead and does not try to generate sidebar links based on SCM instances. Which makes sense because this code is in BitbucketSCMSource.retrieveActions, which overrides SCMSource.retrieveActions. In contrast, the Bitbucket Server Integration plugin generates sidebar links in BitbucketJobLinkActionFactory, which implements the TransientActionFactory extension point so it can be called even without an SCMSource.

The Bitbucket Branch Source plugin also creates BitbucketLink instances in the BitbucketSCMNavigator.retrieveActions method. The BitbucketSCMNavigator class is for things that contain multiple repositories, like projects in Bitbucket Server or workspaces in Bitbucket Cloud. So, that one does not generate sidebar links from SCM instances, either.

kon, I think you are wright about jenkins.branch.NameEncoder. I have simmilar issue with Jira steps plugin
In comment footer plugin adds same %252F instead of %2F. But i have not anough expirience in java to discover root issue
This switch key could be the reason