How to get commit history for just one branch?

You can use a range to do that.

git log master..

If you've checked out your my_experiment branch. This will compare where master is at to HEAD (the tip of my_experiment).

The git merge-base command can be used to find a common ancestor. So if my_experiment has not been merged into master yet and my_experiment was created from master you could:

git log --oneline `git merge-base my_experiment master`..my_experiment

I think an option for your purposes is git log --oneline --decorate. This lets you know the checked commit, and the top commits for each branch that you have in your story line. By doing this, you have a nice view on the structure of your repo and the commits associated to a specific branch. I think reading this might help.

Note: if you limit that log to the last n commit (last 3 commits for instance, git log -3), make sure to put a space between 'n' and your branch:

git log -3 master..

Before Git 2.1 (August 2014), this mistake: git log -3master.. would actually show you the last 3 commits of the current branch (here my_experiment), ignoring the master limit (meaning if my_experiment contains only one commit, 3 would still be listed, 2 of them from master)

See commit e3fa568 by Junio C Hamano (gitster):

revision: parse "git log -<count>" more carefully

This mistyped command line simply ignores "master" and ends up showing two commits from the current HEAD:

$ git log -2master

because we feed "2master" to atoi() without making sure that the whole string is parsed as an integer.

Use the strtol_i() helper function instead.