git-squash

#!/bin/bash

# Sqash all commits in upstream..HEAD to a single commit.

ONTO=$(git rev-parse --abbrev-ref --symbolic-full-name @{u} 2>/dev/null)
if [ -n "$ONTO" ]; then
  BEHIND=$(git rev-list --left-right --count $ONTO...@ | cut -f1)
  if [ $BEHIND != "0" ]; then
    echo "$ONTO: behind $BEHIND"
    ONTO=
  fi
fi

read -p "Squash from? [$ONTO] " OUT
ONTO=${OUT:-$ONTO}
[ -n "$ONTO" ] || exit 1

FIRST=$(git rev-list $ONTO.. | tail -1)
[ -n "$FIRST" ] || exit 1

MSG=$(git show -s --format=%B $FIRST | head -1)
[ -n "$MSG" ] || exit 1

read -p "Commit message? [$MSG] " OUT
MSG=${OUT:-$MSG}
[ -n "$MSG" ] || exit 1

echo ">>> git reset --soft $ONTO"
git reset --soft $ONTO

echo ">>> git commit -m \"$MSG\""
git commit -m "$MSG"