How to list branches that contain another branch in git

A branch name is just a fancy pointer to a given commit (in other words, it's a commitish), so you can look for branches that contain it with the --contains option:

$ git branch --contains my_branch

And if you want to check remote branches as well, you can add the -r flag:

$ git branch -r --contains my_branch

Sounds like you want to know about git branch --contains whatever-branch. Use -r if you want to check remote branches as well.