How can I check whether a branch has been merged into another branch?

Question

In command line, how can I check whether a branch has been merged into another branch, and if yes, find out which branch it has been merged into?

Answer 1

git branch --contains <branch>

will print all local branches where the commit labelled by <branch> is an ancestor.

Answer 2

With --contains, shows only the branches that contain the named commit (in other words, the branches whose tip commits are descendants of the named commit)

--contains []
Only list branches which contain the specified commit (HEAD if not specified)

git branch --contains <commit/tag/branch>