Add ui.strict config item.
This turns off command matching by unambiguous prefix, and is a good
thing if you want to write future-proof scripts.
This fixes issue 314.
Is there an error message when trying to diff non-existing files?
found: No such file or directory
not: No such file or directory
Is there an error message when trying to add non-existing files?
found: No such file or directory
not: No such file or directory