Here is my transcript from trying to merge my bugfix branch onto my master branch in preparation to push it upstream. There have been some upstream changes pulled into maste
With regards to Joshua Hogendorn's answer: it seems to me that leaving Xcode open while working on the repository with git leads to these problems. It even led to a situation where git committed something that I thought to have stashed (and still had afterwards) but Xcode just wrote to the filesystem right during the rebase.
So: Close your Xcode project before you work on the repo with git if you want to be safe, and then you probably don't need the core.trustctime false setting.