Git alias for fixing up a commit

.gitconfig

[alias]

    fixup = "!f() {                                                                                                                                        \
  git diff --cached --quiet && echo \"Nothing is staged\" && exit 1;                                                                                       \
  fixup_commit=$(git log --oneline | fzf --height=40% --layout=reverse --prompt='git log>' --with-nth='2..' --preview='git show --color=always {1}');      \
  echo \"Amending commit: $fixup_commit\";                                                                                                                 \
  fixup_commit_sha=$(echo $fixup_commit | awk '{print $1}');                                                                                               \
  git commit --fixup=$fixup_commit_sha;                                                                                                                    \
  git rebase --update-refs --autosquash -i $fixup_commit_sha^1;                                                                                            \
};                                                                                                                                                         \
f"
    fixup2 = "!f() {                                                                                                                                       \
  git diff --cached --quiet && echo \"Nothing is staged\" && exit 1;                                                                                       \
  local filter;                                                                                                                                            \
  if [ -n $@ ] && [ -e $ ]; then                                                                                                                           \
    filter=\"-- $@\";                                                                                                                                      \
  fi;                                                                                                                                                      \
  fixup_commit=$(git log                                                                                                                                   \
        --graph --color=always --abbrev=7                                                                                                                  \
        --format=\"%C(auto)%h%d - %C(bold green)(%ar)%C(reset) %C(white)%s%C(reset) %C(dim white)- %an%C(reset)\" $@ |                                     \
            fzf --ansi --no-sort --layout=reverse --tiebreak=index                                                                                         \
                --preview=\"f() { set -- \\$(echo -- \\$@ | rg -o '\\b[a-f0-9]{7,}\\b'); [ \\$# -eq 0 ] || git show --color=always \\$1 $filter; }; f {}\" \
                --preview-window=right:60%);                                                                                                               \
  echo \"Amending commit: $fixup_commit\";                                                                                                                 \
  fixup_commit_sha=$(echo $fixup_commit | rg -o '\\b[a-f0-9]{7,}\\b');                                                                                     \
  echo \"SHA: '$fixup_commit_sha'\";                                                                                                                       \
  git commit --fixup=$fixup_commit_sha;                                                                                                                    \
  git rebase --update-refs --autosquash -i $fixup_commit_sha^1;                                                                                            \
};                                                                                                                                                         \
f"

README.md

Assuming you have fzf installed. Tested on Ubuntu 20.04.

Adapted from https://twitter.com/ericniebler/status/1789843284027728166 and https://twitter.com/foonathan/status/1789943474994745494

This is helpful in a situation where you mean to ammend a commit back in history (not the last one, for that one you can just git commit --amend).

After staging some changes:

• This opens a fzf picker to select the commit you want to amend with your changes, with a preview pane that shows the commit detail when you select one
• This git commit --fixup=<commit>
  • see git docs for --fixup
  • This new fixup! will be automatically squashed with the target commit during the rebase below
• This performs a git rebase --update-refs --autosquash -i <commit_before>
  • --autosquash squashes the fixup! commit
  • --update-refs: Automatically force-update any branches that point to commits that are being rebased

fixup, simpler

fixup2, with a graph