Summary of changes between two commits of branches in Git

git diff --shortstat branch1..branch2

This will show the differences between branch1 and branch2 but only output a short summary, for example:

2 files changed, 165 insertions(+), 5 deletions(-)

There are other ways to specify the commit range, git diff will look at, you can read about them in the manual.

Try git diff --stat. And there's the even shorter --shortstat.

e.g. on branch master type git diff --stat otherbranchname