After working for several weeks with a half dozen different branches and merges, on both my laptop and work and my desktop at home, my history has gotten a bit convoluted. For example, I just did a fetch, then merged master with origin/master. Now, when I do git show-branches, the output looks like this:

! [login] Changed domain name.
 ! [master] Merge remote branch 'origin/master'
  ! [migrate-1.9] Migrating to 1.9.1 on Heroku
   ! [rebase-master] Merge remote branch 'origin/master'
----
 - - [master] Merge remote branch 'origin/master'
 + + [master^2] A bit of re-arranging and cleanup.
 - - [master^2^] Merge branch 'rpx-login'
 + + [master^2^^2] Commented out some debug logging.
 + + [master^2^^2^] Monkey-patched Rack::Request#ip
 + + [master^2^^2~2] dump each request to log
....

I would like to clean this up with a git rebase. I created a new branch, rebase-master, for this purpose, and on this branch tried git rebase <common-ancestor>. However, I have to resolve many conflicts, and the end result on branch rebase-master no longer matches the corresponding version on master, which has already been tested and works!

I thought I saw a solution to this somewhere but can't find it anymore. Does anyone know how to do this? Or will these convoluted ref names go away when I start deleting un-needed branches that I have already merged with?

I am the sole developer on this project, so there is no one else who will be affected.