Refactored: split CAppUtils::Merge()

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Add "Retry" button for Merge

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Refactored: split CAppUtils::Pull()

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Add "Retry" button for Pull

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Refactored for Switch command

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>