Question

I have a tree that looks like the following

  B
 / \
A   D
 \ /
  C

B and C don’t conflict. What I want is it to show in my history as A-B-C-D.

How can I do this in git? I’ve searched but I can’t find an answer I feel applies. I’m concerned to make a change because I don’t want to make things worse and I don’t know how I would undo it (is there a way to undo the last git command in git?)

Answer 1

If you want to test things out, simply clone your repository and play in the clone.

$ git clone your_repo test_repo
$ cd test_repo

In your case, D should just be a merge commit, which doesn’t contain much if B and C don’t conflict. So a simple rebase will work

$ git rebase branch_of_B branch_of_C

Try this in an empty repository:

echo A > file1
git add file1
git commit -m A
git checkout -b B
echo B > file2
git add file2
git commit -m B
git checkout master
git checkout -b C
echo C > file3
git add file3
git commit -m C
git checkout -b merge_branch
git merge B
echo D > file4
git add file4
git commit -m D

You now have this (run gitk --all):

   B
  / \
 A   M - D
  \ /
   C

and you’re on D. You can issue

$ git rebase B
First, rewinding head to replay your work on top of it...
Applying: C
Applying: D

And you’re left with:

A - B - C' - D'
 \
  C

with C' and D' identical to C and D in terms of “contents”. If you want to clean up, you can remove branch C in this example, but you’ll have to force it since that will make the original C commit dangle.

$ git branch -D C