Reset/revert a whole branch to another branches state?

Question

I have a branch A and a branch B (and some other branches).

Lets say A's commit history looks like:

• commit 5
• commit 4
• commit 3
• ...

And B's commit history:

• some other commit
• commit 4
• merge of other stuff from branch C (into branch B)
• commit 3
• ...

Basically what I want is to "delete" all changes made by the commits some other commit and merge of other stuff from branch C to branch B.

I want the working tree of branch B to be exactly the same like branch A's working tree.

How do I achieve this?

Answer 1

One way to achieve this is through git reset. While on branch B execute

git reset --hard A 

Thereafter, branch B points to the head-commit of A. The --hard option resets the index and working tree so that all tracked files are reset to the version in branch A. The old HEAD commit-ID of A is stored in .git/ORIG_HEAD in order to allow undoing the change.

Alternatively - while not on branch B - you can delete branch B and re-created it like this:

git branch -d B     # delete branch B git branch B A      # re-create branch B and let it point to the commit of branch A 

Other than the first suggestion, this will leave the index and working tree untouched.

Answer 2

If you want your branch B to look exactly like branch A. You could just do a reset --hard

git checkout branch-B  git reset --hard branch-A 

Be careful you will lose commits in this case. Your branch-B will look exactly like branch-A, whatever commits were made to branch-B, that were not present in branch-A, will be lost. Also if branch-B is shared with other people, its not recommended to perform this operation.

In that case you could try reverting the commits you don't want in branch-B

git revert <sha-of-"some other commit"> git revert <sha-of-"merge of other stuff from branch C (into branch B)">  

The second commit looks like a merge commit so you might have to pass the parent as well.

 git revert <sha-of-"merge of other stuff from branch C (into branch B)"> -m1