There is no "Integrate Branch" action in any of feature branches' builds. The following are from `svn info`:

dev1:
Path: .
Working Copy Root Path: /var/lib/jenkins/jobs/xxxx-dev1/workspace
URL: https://192.168.3.15/svn/xxxx/branches/dev1
Repository Root: https://192.168.3.15/svn/xxxx
Repository UUID: d0eb5361-05ce-7c4b-8453-cbb3c9b96fe4
Revision: 131
Node Kind: directory
Schedule: normal

trunk:
Path: .
Working Copy Root Path: /var/lib/jenkins/jobs/xxxx/workspace
URL: https://192.168.3.15/svn/xxxx/trunk
Repository Root: https://192.168.3.15/svn/xxxx
Repository UUID: d0eb5361-05ce-7c4b-8453-cbb3c9b96fe4
Revision: 129
Node Kind: directory
Schedule: normal

What I've done was create a Jenkins job for the trunk. Then create a the dev1
branch in Feature Branches. Then make a change to the README.md, perform a build,
all on dev1. Then go to last build. Yet can't see the Integrate Branch action.

Not sure if it's related, I've tried adding the Integrate to upstream upon successful build post-build action,
and got an exception at the end of a (successful) build:

ERROR: Publisher jenkins.plugins.svnmerge.IntegrationPublisher aborted due to exception
java.lang.NullPointerException
at jenkins.plugins.svnmerge.IntegrateAction.perform(IntegrateAction.java:183)
at jenkins.plugins.svnmerge.IntegrateAction.perform(IntegrateAction.java:172)
at jenkins.plugins.svnmerge.IntegrationPublisher.perform(IntegrationPublisher.java:51)
at hudson.tasks.BuildStepMonitor$2.perform(BuildStepMonitor.java:32)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:770)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:734)
at hudson.model.Build$BuildExecution.post2(Build.java:183)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:683)
at hudson.model.Run.execute(Run.java:1784)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:89)
at hudson.model.Executor.run(Executor.java:240)

I've double checked the Upstream project name is correct. Also, the branch job is created with "Feature Branch".

In the "Configure" of branch job:
"This project builds a Subversion feature branch" is checked;
"Upstream project name" is "xxxx".

In the Status page of branch job:
"Subversion Merge Tracking
This project is a feature branch of xxxx"

Clicking the job link goes to the master job "xxxx", as expected.

In the "Configure" of master job:
"Accept Integration from Subversion feature branches" is checked.

In the "Feature Branches" of master job:
"Existing Feature Branches
xxxx-dev1"

Clicking the job name goes to the branch job, as expected.

The svn repo is a fresh one, just for trying out the Jenkins. There is no other sources in it.

I've double checked with:
svn propget svn:externals
Which returns empty.