Make sure rebase is never executed on CLI on pull

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Disable "rebase after" checkbox if remote is a URL

Signed-off-by: Sven Strickroth <email@cs-ware.de>
FetchDlg: Disable "rebase after" checkbox if "all remotes" is selected

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