Why SourceGit stops to remember the last selected handling method of uncommitted local changes

Since the situation I was worried about still occurred, I decided to roll back this feature.

• Applying the same operation to local change each time is not the correct way.
• Users are likely to mis-operate without noticing.
• After local unstaged and unstashed changes are wrongly deleted, there is no way to recover them. This is a very serious matter.

See #977