Transplant commits from one source to another

git-transplant

#!/bin/bash

if [[ $# -ne 2 ]]; then
    cat >&2 <<EOF
Transplant a branch from one root to another.
Handy if you've done a squash-merge and need to rebase <from> the old branch <onto> the new master.
Usage:
    git transplant <from> <to>

where:
  from: The commit or branch where your 'keep' commits will start from. The <from> commit itself is NOT kept, only its children

  to: The branch onto which the commits between (<from>..HEAD] will be rebased.
EOF
    exit 1
fi

from="$1"
to="$2"

echo "Transplanting these commits:"
git log --pretty=format:'%Cblue%h%Creset %Cgreen%<(15)%ad%Creset | %s%d [%C(yellow)%an%Creset] %C(cyan)%d%Creset' --date=relative "$from"..HEAD
echo
echo '================================================================================'
echo
echo "Which were previously based on:"
git log -1 --pretty=format:'%Cblue%h%Creset %Cgreen%<(15)%ad%Creset | %s%d [%C(yellow)%an%Creset] %C(cyan)%d%Creset' --date=relative -1 "$from"
echo
echo '================================================================================'
echo
echo "Onto:"
echo
git log -1 --pretty=format:'%Cblue%h%Creset %Cgreen%<(15)%ad%Creset | %s%d [%C(yellow)%an%Creset] %C(cyan)%d%Creset' --date=relative -1 "$to"
echo
echo '================================================================================'
echo
echo "Which will remove the following commits:"
echo
git log --pretty=format:'%Cblue%h%Creset %Cgreen%<(15)%ad%Creset | %s%d [%C(yellow)%an%Creset] %C(cyan)%d%Creset' --date=relative "$to".."$from"
echo
echo '================================================================================'
echo

read -p "Continue? (y/n)
" -n 1 -r
echo
if [[ ! $REPLY =~ ^[Yy]$ ]]; then exit 1; fi
git rebase --onto "$to" "$from"

See also https://blog.adamspiers.org/2018/06/14/git-auto-magic/