Major Description
I tried to come up with a test case that would result in the VersionablePathHook running into a CommitFailedException upon accessing the version history and found out that this will never occur. In other words, the whole logic to collection CommitFailedException in VersionablePathHook is redundant.
What I found was that ReadWriteVersionManager.getOrCreateVersionHistory is defined to potentially throw the exception on calling createVersion, which is only triggered if the version history node contains no jcr:rootVersion child. However, createVersion will never throw CommitFailedException if the root version is created as the exception may only occur upon populating the jcr:frozenNode.
Long story short: introducing ReadWriteVersionManager.createRootVersion and calling it from getOrCreateVersionHistory would simplify createVersion, make the exception declaration redundant and spare us the unused but prominent exception handling code in VersionablePathHook.
stillalex, mreutegg, i would appreciate if you could review the proposed changes to VersionablePathHook and ReadWriteVersionManager.