I didn’t find git tags that distinguish 3.4RC1, 3.4RC2, etc for the ardupilot source code. I only found a 3.4 branch. The only way I found to find the RC1 version was to look for Copter: 3.4-rc1 release notes, but that’s not a guarantee that it only RC1 code changes are before that checkin. Is there another way to find the release tags?
I think there are no tags for release candidates.
If you are searching for a commit that introduced / fixed a bug this might help:
I ended up forking ardupilot and creating my own branch tags.