Search git status preview updates

• rewrite status parsing logic and fix bug with renames (8f0f134)
• show diff type header in yellow and fix color bleeding (785df55)
• add tests for preview logic (fe06393)

Search git history update

Don't merge history when in private mode (#245 and a79dc75). Calling history merge in private mode (fish --private) clears the session history. So if you execute the search history function while in private mode, there is no history to search. This has now been fixed