I am on branch mybranch1. mybranch2 is forked from mybranch1 and changes were made in mybranch2.
Then, while on mybranch1, I have done git merge --no-commit mybranch2 It shows there were conflicts while merging.
Now I want to discard everything (the merge command) so that mybranch1 is back to what it was before. I have no idea how do I go about this.
Latest Git:
git merge --abort This attempts to reset your working copy to whatever state it was in before the merge. That means that it should restore any uncommitted changes from before the merge, although it cannot always do so reliably. Generally you shouldn't merge with uncommitted changes anyway.
Prior to version 1.7.4:
git reset --merge This is older syntax but does the same as the above.
Prior to version 1.6.2:
git reset --hard which removes all uncommitted changes, including the uncommitted merge. Sometimes this behaviour is useful even in newer versions of Git that support the above commands.
git reset --merge even in more recent versions. I've had git merge --abort error out (making no changes) where git reset --merge succeeds (and does the right thing) in git 2.2.1.
git merge --abort followed by git reset --merge when having automerge conflict from popping my stash.
git merge --abort works for me, however I found myself in a situation where I checked out in a detached HEAD state, and one of my files had a "both modified" state. I wanted to discard everything and get back to a branch, I had to git reset --hard, git merge --abort told me there was no merge to abort, (MERGE_HEAD missing).
git merge --abort isn't able to bring you back your previous state, and in that case the "older syntax" git reset --hard does the trick.Actually, it is worth noting 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.
git stash apply on a wrong branch, and git merge --abort did nothing (no MERGE_HEAD), while git reset --merge did the trick.
git merge --abort is the new command for git reset --merge and I ran into the same issue as @geomaster this was super helpful thanks!
git checkout --merge which resulted in conflicts, ended up losing data. git docs say it will keep worktree files which differ from the index, which it does, but for any conflicted file, you get the checkout version, and the worktree version is completely lost.Assuming you are using the latest git,
git merge --abort If using latest Git,
git merge --abort else this will do the job in older git versions
git reset --merge or
git reset --hard 
git version 2.31.1, that was released later than this comment so I consider it "latest", only git reset --hard worked, and the rest didn't.There are two things you can do first undo merge by command
git merge --abort or
you can go to your previous commit state temporarily by command
git checkout 0d1d7fc32 Since nobody mentioned this before, if you get this error
fatal: Could not reset index file to revision 'HEAD'. when trying the above methods you can try adding the files (staging them) and then instead of committing just do git stash you can use the -m flag and give it a tag so you know if you do by chance need to recover that last state you can find the stash with git stash list.
For me, git reset --merge and git merge --abort failed with above error.
git reset --hard to undo the failed merge.Sourcetree
If you not commit your merge, then just double click on another branch (=checkout) and when sourcetree ask you about discarding all changes then agree
