Undoing git reset?

Question

What's the simplest way to undo the

git reset HEAD~

command? Currently, the only way I can think of is doing a "git clone http://..." from a remote repo.

Answer 1

I was wrong the first time around, so here's the revised version:

Reset only sets the current HEAD-pointer to the specified changeset. When doing a reset HEAD~ you actually just move your master-branch pointer to the previous commit.

To undo the effect you can do

git reset --hard origin/master

assuming, that origin/master was where you pulled/would pull from.

gitk --all is really helpful when solving these kinds of issues.

Answer 2

Short answer:

git reset HEAD@{1}

Long answer:

Git keeps a log of all ref updates (e.g., checkout, reset, commit, merge). You can view it by typing:

git reflog

Somewhere in this list is the commit that you lost. Let's say you just typed git reset HEAD~ and want to undo it. My reflog looks like this:

$ git reflog
3f6db14 HEAD@{0}: HEAD~: updating HEAD
d27924e HEAD@{1}: checkout: moving from d27924e0fe16776f0d0f1ee2933a0334a4787b4c
[...]

The first line says that HEAD 0 positions ago (in other words, the current position) is 3f6db14; it was obtained by resetting to HEAD~. The second line says that HEAD 1 position ago (in other words, the state before the reset) is d27924e. It was obtained by checking out a particular commit (though that's not important right now). So, to undo the reset, run git reset HEAD@{1} (or git reset d27924e).

If, on the other hand, you've run some other commands since then that update HEAD, the commit you won't won't be at the top of the list, and you'll need to search through the reflog.

One final note: It may be easier to look at the reflog for the specific branch you want to un-reset, say master, rather than HEAD:

$ git reflog show master
c24138b master@{0}: merge origin/master: Fast-forward
90a2bf9 master@{1}: merge origin/master: Fast-forward
[...]

This should have less noise it in than the general HEAD reflog.