Optimize by forking Default Branch Only

[shinigami-777]

Towards #104
Set the defaultforkonly to true with GHRepositoryForkBuilder to in place of fork() (fork was also deprecated in the recent release) to optimize forking process.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[shinigami-777]

The new version github-api-2.0-alpha-3 is released now. I took a try at solving the issue. But the originalRepo.createFork() returns null giving the error
Cannot invoke "org.kohsuke.github.GHRepositoryForkBuilder.organization(org.kohsuke.github.GHOrganization)" because "builder" is null
I can't seem to understand why this is happening. Please take a look.

[jonesbusy]

Please take a look

Adapt the unit tests maybe?

[shinigami-777]

Adapt the unit tests maybe?

Sorry, I somehow completely overlooked this before.
Adjusted them for GHServiceTest.

[shinigami-777]

@jonesbusy When I clone the main branch fresh, the tests are failing the same as this.

[jonesbusy]

Why not bump version until updatecli merge the PR?

We have a contributor that did it on his PR

#673

Don't expect maintainers to give you always the information.

[jonesbusy]

See #733

[shinigami-777]

Thanks. I'm looking into it

[jonesbusy]

Hi, I think the method name defaultbranchonlyfork should be renamed to something like fork. That's enough since it's a private method and there will not be other way to fork

Then I think we are good to merge

Supersedes #710