如何撤消git merge squash？

Question

I have just done a

git merge --squash feature-branch

into my develop branch.

The problem is that the above command updated the head without creating a new commit. My intention was to create one single commit to apply to the head of develop .

So in short, the log for the develop branch before and after the merge are exactly the same.

Is there a way to revert back develop to what it was before the git merge ?

Thank you.

Solution

Based on the comment from Dan D. and the accepted answer below I was able to resolve my problem. See below what I did in case you are in the same boat:

1 - I ran git reflog and it listed all the commits and checkouts I did with my develop branch.

2 - Instead of doing a git reset HEAD@{1} as suggested, I found the number when I did the last commit to develop that I wanted to keep. In my case it was HEAD@{188} . So I typed git reset HEAD@{188} .

3 - I ran a git log and it had a clean log showing only the commits I had before I did the wrong merge.

4 - I ran git add -A . to stage all the new files created during my feature development.

5 - I ran git commit -m "install feature-x"

6 - As a result now I have branch develop with the correct files and the log is clean - showing only one commit for all the changes I did during the development of feature-x .

I still need to find out why my original git merge --squash feature-branch did not work as intended.

Solution 2

Mark Longair's answer is a definitive solution to my problem. I have just tested it and it works. See below the process I am using now to squash all the internal commits within a feature-branch and include just one commit to the develop branch:

git checkout develop
git merge --squash feature-branch
git commit -m "install of feature-branch"

The above sequence works like a charm.

Answer 1

If you run git merge --squash <other-branch> the working tree and index are updated with what the result of the merge would be, but it doesn't create the commit. All you need to do is to run:

git commit

However, if you change your mind before committing and just want to abort the merge, you can simply run:

git reset --merge

You don't need to use the reflog.

Answer 2

If you change your mind before committing, you have these options:

Abort the merge with modern git syntax:

git merge --abort

And with older syntax:

git reset --merge

And really old-school:

git reset --hard

But actually, it is worth noticing that git merge --abort is only equivalent to git reset --merge given that MERGE_HEAD is present. This can be read in the git help for merge command.

git merge --abort is equivalent to git reset --merge when MERGE_HEAD is present.

After a failed merge, when there is no MERGE_HEAD , the failed merge can be undone with git reset --merge but not necessarily with git merge --abort , so they are not only old and new syntax for the same thing . Personally I find git reset --merge much more useful in everyday work.