Fix UITest broken by 37524595ed8

Change-Id: I506a5986167a7c4d50075b4beee4f5f640a76cbf
Signed-off-by: Stefan Lay <stefan.lay@sap.com>
Check for uncommitted changes before squashing commits.

This checks for uncommitted changes in the repository and prompts the
user to clean them up before Modify > Squash from the history view
context menu is actually executed.

Bug: 431341
Change-Id: I2af54978a0400fa5d5a0a82ba91f37e0d7bcb201
Signed-off-by: Maik Schreiber <blizzy@blizzy.de>