Editing, amending, or squashing the root commit in a Git repositoryEdit

Editing or amending

From the Git FAQ, "How do I edit the root commit":

$ git tag oldroot SHA1_OF_OLD_ROOT_COMMIT # tag the old root
$ git checkout -b newroot oldroot         # create a temporary branch wherein to create the modified root
$ git commit --amend                      # after editing, staging etc as desired
$ git checkout @{-1}                      # back to previous branch
$ git rebase --onto newroot oldroot       # rebase everything on top of amended root
$ git branch -d newroot                   # clean up temporary branch
$ git tag -d oldroot                      # and temporary tag

Squashing

From:

• http://stackoverflow.com/questions/598672/git-how-to-squash-the-first-two-commits
• http://stackoverflow.com/questions/435646/how-do-i-combine-the-first-two-commits-of-a-git-repository

Based on this history:

old
root
v
A---B---C---D---etc
    ^
    new
    root

We want to squash A and B together to produce a new root commit, AB:

AB---C'---D'---etc

$ git log --oneline --reverse   # inspect SHA1 of old and new roots
$ A=12bed43a                    # old root
$ B=4dde1290                    # new root
$ git show $B                   # take note of commit message
$ git checkout $B               # detached head corresponding to B
$ git reset --soft $A           # leave index and working tree from B
$ git commit --amend            # commit message for A shown, merge or replace with commit message from B
$ git tag newroot               # remember this for later
$ git checkout @{-1}            # go back to last branch (eg. master or whatever)
$ git rebase --onto newroot $B  # replay all commits after B onto new initial commit
$ git tag -d newroot            # remove temporary tag