Operations within the app often block each other's access to .git/index.lock

A persistent and frequent complaint is that I so often get failed operations in SourceTree because of the famous .git/index.lock permission denied message. Obviously, this can't be avoided if I'm doing something with a working copy in another app (like Terminal) at the same time. However, I should never get this for operations only within SourceTree, whether manual or automatic.

For example, often I'm staging chunks of individual files for a commit. Frequently I'll get an alert that the operation failed and have to try again. Usually, this is because SourceTree is updating something in the background. The app should do some sort of coordination before attempting to modify a working copy, so this error never gets presented to users.