Git: Undo the last commit

Run git reset HEAD~ or alias it to git undo. Bonus: how to use the commit message from the undoed commit.

Undo the last/previous/most recent commit:

git reset HEAD~

Afterwards, to use the commit message from the undoed commit:

# -C <commit>
# --reuse-message=<commit>
#
#     Take an existing commit object,
#     and reuse the log message and the authorship information (including the timestamp)
#     when creating the commit.
#
# -c <commit>
# --reedit-message=<commit>
#
#     Like -C, but with -c the editor is invoked,
#     so that the user can further edit the commit message.

git commit -c ORIG_HEAD

If using my git aliases:

git undo

# Use the commit message from the undoed commit
git redo