How to undo a git merge with conflicts

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.

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.

Assuming you are using the latest git,

git merge --abort