Once a branch has been merged if the commit ID no longer equals that of
the pulls ref commit id don't offer to delete the branch on the pull screen
and don't list it as merged on branches.
Fix#9201
When looking at the pull page we should also get the commits from the refs/pulls/x/head
Fix#9158
* implemented missing 'delete' push webhooks
moreover created ActionDeleteBranch and ActionDeleteTag
* add CommitRepoAction tests for tag/branch creation/deletion
* fixed error where push webhook not called if is new branch or tag
removed unnecessary code
* moved prepare unit test environment into separate method to be used across unit tests
* add missing if clause in pushUpdate
Signed-off-by: David Schneiderbauer <dschneiderbauer@gmail.com>