Add compare branches endpoint to API

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add some tests to compare api

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Expose timeout and same_ref compare fields

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Better specs for Compare API

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'compare-api' into 'master'

Compare api

Fixes #1165