git: programmatically know by how much the branch is ahead/behind a remote branch

Question

I would like to extract the information that is printed after a git status, which looks like:

# On branch master
# Your branch is ahead of \'origin/         


        

Answer 1

Edit: My original answer was actually not very good because it relied on the user to have a remote called "origin". It also failed if the current branch was had a tracking branch besides origin-head. These flaws essentially made it useless. However, the answer by @araqnid is not the most efficient method and the way he arrives at $tracking_branch is less than strait forward. The most efficient (fastest) method I have found to get the same functionality is the following:

# get the tracking-branch name
tracking_branch=$(git for-each-ref --format='%(upstream:short)' $(git symbolic-ref -q HEAD))
# creates global variables $1 and $2 based on left vs. right tracking
# inspired by @adam_spiers
set -- $(git rev-list --left-right --count $tracking_branch...HEAD)
behind=$1
ahead=$2

---

original answer: (inferior, but given for clarity)

Perhaps the simplest method I could find (inspired by @insidepower)

# count the number of logs
behind=$(git log --oneline HEAD..origin | wc -l)
ahead=$( git log --oneline origin..HEAD | wc -l)

I had previously been using the method of @araqnid, but now I think I'll move some of my scripts to this method since it is much simpler. This should work on any unix system.

Answer 2

Why wouldn't this work:

#!/bin/sh
git diff origin/master..HEAD --quiet --exit-code
RETVAL=$?
if [ $RETVAL -gt 0 ]; then
    echo "You need to git push!"
else
    echo "No git push necessary!"
fi 

Answer 3

You can try git branch -v -v. With -v flag given twice, it outputs names of upstream branches. Sample output:

* devel  7a5ff2c [origin/devel: ahead 1] smaller file status overlay icons
  master 37ca389 [origin/master] initial project check-in.

I think this format is more stable than git status output.

Answer 4

The top chunk of code in araqnid's answer doesn't work for me, so maybe something in git has changed since it was written 18 months ago. It works if I change:

tracking_branch=refs/remotes/$remote/$remote_branch

to

tracking_branch=$remote/$remote_branch

However there is still an issue when tracking a local branch, in which case you have to trim the remote part (which becomes '.'):

tracking_branch=${tracking_branch#./}

Then you can programmatically obtain the number of revisions behind and ahead as follows:

set -- `git rev-list --left-right --count $tracking_branch...HEAD`
behind="$1"
ahead="$2"

I've written scripts to do all that (and more - e.g. they can also attempt to spot remotes on the other side of a git-svn bridge), and published them in my git-config repository on github. For example, here's my git-compare-upstream. See the README for installation instructions and other handy related scripts.