Unbreak support Windows XP

Fixes a regression of 48f06fb7fb818bea392f9e03a7785ed4b55248c9.

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Update libgit2

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Fixed issue #2179: Revision comparisons against HEAD should not generate temporary files (allow to compare to working tree)

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Optimize positioning of button

Signed-off-by: Sven Strickroth <email@cs-ware.de>