Continual background diffs conflict with user requests.

This has been occuring for some time, but had not previously been able to confirm it was not another git tool.  However, it can happen on a computer with no other git instances installed.

When trying to do complex activities such as rebase interactive, where the UI shows diffs of items, the diff refresh for the page can cause a lock file which can still be present when the OK button is pressed.  This causes the request to fail, and then the user has to do it again, at which time it can fail again (or as it is a race condition, possibly work).

This can impact adding lines, sections, or entire files via the UI as well.  Where the update of the diffs can still be occuring when the add happens.

By increasing the maximum diff size and testing with files with more changes, you increase the likelihood this error will occur.