git: rewrite history: reorder and merge commits

You want to do an interactive rebase.

The first thing I like to do when trying out git commands is to make a backup copy of my branch:

$ git branch my-backup-branch

Let's say that your A1 commit has a hash of 152274b. Try this:

$ git rebase -i 152274b^

That command will bring up your editor (usually vim) with something like this:

pick 152274b A1pick 14b0838 B1pick 661b993 A2pick a6510db B2pick 557e171 A3pick 85da0e4 B3# Rebase 39a47e4..85da0e4 onto 39a47e4## Commands:#  p, pick = use commit#  e, edit = use commit, but stop for amending#  s, squash = use commit, but meld into previous commit## If you remove a line here THAT COMMIT WILL BE LOST.# However, if you remove everything, the rebase will be aborted.#

From here you can change the order of the commits, delete them entirely and even squash them. In this example, you probably want to move and squash like this:

pick 152274b A1squash 661b993 A2squash 557e171 A3pick 14b0838 B1squash a6510db B2squash 85da0e4 B3

Give it a try. If you end up in a state that you didn't want, you can always go back to the state you saved in your backup branch:

$ git reset --hard my-backup-branch