reverting a git changeset

I accidentally committed a changeset without a description and wanted to fix it. As I was pushing enter I realized that I didn’t want to commit yet. I have not pushed anywhere – an important requirement for this kind of revert.

I basically want to do a bk fix -c (if I recall my bk correctly).

Since git revert pollutes the history, it is not the right thing to do here since the bad changeset was not pushed. But it would be the right thing to do had I pushed my change.

Here is the right thing to do:

    1 $  git diff HEAD~1 > ../last.patch
    2 $  git checkout -f -b tmp HEAD
    3 $  git branch -D master
    4 $  git checkout -f -b master HEAD~1
    5 $  git branch -D tmp
    6 $  patch -p1 < ../last.patch 
    7 $  cg commit net/ipsec/ipsec_ipcomp.c

(Warning: this is actually completely unnecessary, see below)

Here is what actually happens:

1. backup the work that we had done into a patch.
2. get of master onto a temporary branch, tmp, which just allows us to…
3. delete the current master, so that we can…
4. backup one revision and create a new master branch before the bad commit.
5. now delete the tmp branch.
6. revert the change we want to commit, and finally
7. commit the changes
   … but this time comment them :)

NOTE: I think one or two steps can be carved off by using git branch instead of git checkout. If you find a better way, I would love to hear about it.

UPDATE: It turns out that you can do this with git commit --amend in new git releases.

Final Update: Roberto Aguilar pointed out that I should have used git reset… in retrospect, what was I thinking!?