Re: Undo last commit?

On Sun, 19 Jun 2011, Jonathan Nieder wrote:

Jakub Narebski wrote:

quoted

Mike [off-list ref] writes:

quoted

quoted

% git reset --hard HEAD~1

Errr... here you screwed up.  This reset state of you working area to
the state at last commit, removing all your changes to tracked files.

Or rather, here we screwed up.  Jakub and others gave some useful
advice about how to recover, so let's consider how the UI or
documentation could be improved to prevent it from happening again.

* In this example if I understand correctly then the index contained
  some useful information, perhaps about a larger commit intended for
  later.  To preserve that, you could have used

	git reset --soft HEAD~1

  which would _just_ undo the effect of "git commit", leaving the index
  and worktree alone.

Another issue is that Mike haven't realized that `--amend' option can be
used *in combination* with other "git commit" options, which means that
the solution to his problem was using "git commit" as it should have
been done, but with '--amend' added.
 
I'm not sure if git documentation talks about 'git reset --soft HEAD^',
and when to use it; from what I remember it encourages use of 
'git commit --amend' instead (which was I guess most often used reason
of using soft reset before there was '--amend').

* Another situation that comes up from time to time is making a change
  that just turned out to be a bad idea.  After commiting it, you might
  want to discard the erroneous change, like so:

	git reset --keep HEAD~1

  The "--keep" option uses some safeguards to make sure that only the
  committed change gets discarded, instead of clobbering local changes
  at the same time.

* In the early days of git, the "--keep" option did not exist.  So a lot
  of old documentation recommends to do

	git reset --hard HEAD~1

  which is the same if you don't have any local changes.

Yes, it would be good idea to examine git documentation (tutorials,
user's manual, manpages, perhaps "Git Community Book" and "Pro Git"
too) to encourage use of new safer options of hard reset, namely
'--keep' and '--merge' instead of '--hard'.
 
-- 
Jakub Narebski
Poland