How can I know if a branch has been already merged into master?

There is a graphical interface solution as well. Just type

gitk --all

A new application window will prompt with a graphical representation of your whole repo, where it is very easy to realize if a branch was already merged or not

You can use the git merge-base command to find the latest common commit between the two branches. If that commit is the same as your branch head, then the branch has been completely merged.

Note that git branch -d does this sort of thing already because it will refuse to delete a branch that hasn't already been completely merged.

In order to verify which branches are merged into master you should use these commands:

• git branch <flag[-r/-a/none]> --merged master list of all branches merged into master.
• git branch <flag[-r/-a/none]> --merged master | wc -l count number of all branches merged into master.

Flags Are:

• -a flag - (all) showing remote and local branches
• -r flag - (remote) showing remote branches only
• <emptyFlag> - showing local branches only

for example: git branch -r --merged master will show you all remote repositories merged into master.

git branch --merged master lists branches merged into master

git branch --merged lists branches merged into HEAD (i.e. tip of current branch)

git branch --no-merged lists branches that have not been merged

By default this applies to only the local branches. The -a flag will show both local and remote branches, and the -r flag shows only the remote branches.