[xwiki-devs] Trying to Understand Repositories

I'm just beginning my exploration of XWiki from a development standpoint, and I could use a little help in figuring out the structure of the XWiki source repository in terms of release versions. I see the use of both branches and tags in the Git repository. At this point I guess I really only have two basic questions. What version of a project such as xwiki-platform is supposed to be in the "master" branch? At this point in time, would I be correct in assuming that it is the current state of 4.2M1? IOW, master is always the current status of the upcoming release? If I'm wrong about that, how is the code for 4.2[M1] identified in Git? Beyond that, does Git contain under-development code beyond the next release, and if so how is it identified? My second basic question concerns identifying code in Git that matches a given past (or current) production release. For example, what would I checkout to capture the state of the source code as of the public release of 4.1.3? I see a branch for "stable-4.1.x" and also a tag for "xwiki-platform-4.1.3" (among a surprisingly large number of tags) when looking at the xwiki-platform project, and the distinction is not clear to me. I've been through everything I could find in the wiki and didn't find anything that answered these questions. TIA. --Gary