squashbranch

#!/bin/bash

# Squash all changes on the current branch in one go
# Copyright (c) 2018 Benjamin Holt -- MIT License

if [ "$1" == "-h" -o "$1" == "--help" ]; then
    cat <<USAGE
usage: squashbranch [PARENT]   Squash all changes on the current branch; PARENT
                               defaults to "main".  Current branch must have
                               clean status so local changes don't get scooped
                               up in the squash.  To undo the squash prior to
                               committing:
                               $ git reset --hard && git pull

       squashbranch -h|--help  Print this message and exit
USAGE
    exit 0
fi

Bold=`tput bold`
Off=`tput sgr0`

Status=`git status -s`
if [ "$Status" ]; then
  echo "${Bold}Current branch has uncommitted changes:${Off}"
  echo "This cannot distinguish between changes to be squashed and local or untracked changes; commit changes you want or stash changes you don't (including untracked files)"
  echo "$Status"
  exit 1
fi

Parent="${1:-main}"
BranchName=`git rev-parse --abbrev-ref HEAD`

if [ "$BranchName" == "main" -o "$BranchName" == "master" ]; then
  echo "${Bold}Squashing the $BranchName branch is not generally a good idea${Off}" 1>&2
  exit 1
fi

if [ "$Parent" == "$BranchName" ]; then
  echo "${Bold}Cannot squash $BranchName relative to itself${Off}" 1>&2
  exit 1
fi

BranchPoint=`git merge-base "$Parent" "$BranchName"`
BranchHashes=`git log "$BranchPoint..HEAD" --format=format:%h | tr "\n" " "`
echo "----------------------------------------------------------------------"
echo "${Bold}Squashing back to $BranchPoint:${Off}"
git log "$BranchPoint~1..HEAD" --format=oneline --abbrev-commit  # Include branched commit
echo "----------------------------------------------------------------------"
# echo "${Bold}DIDN'T REALLY SQUASH${Off}" && exit 0  # Early-exit for testing
git reset "$BranchPoint"
git add -A
echo "----------------------------------------------------------------------"
git status
echo "----------------------------------------------------------------------"
echo "${Bold}Squashed:${Off} $BranchHashes"
echo "Now git commit with a message for the single commit and force-push (or undo with 'git reset --hard && git pull')"
###