I only discovered some promotion information accessible through json api: the latest promotion build number (not the build number of the job being promoted) from permalinks:
and eventually information of every promoted build:
But the response does not contain any information related to build number of the origin job being promoted, so I basically cannot tell which build has been promoted by which promotion build, which is exactly the information I want to get.
It would be nice if the following information could be exposed through remote access api:
a) promotion status for each build, and/or
b) a summary/history of all promotion builds with reference to the being promoted build number.