#!/bin/sh

# Switch to the more diverged of master and current dev Emacs branches.
# 
# This automates the process of choosing between the Emacs development
# branch (e.g., 'emacs-27') and 'master' branch when building for use,
# since for use one just wants whichever branch has more unique changes.
# When building for development use, one would choose whichever branch
# is most appropriate for the specific dev work, obviously.

NAME1="master"
NAME2="emacs-27"

git checkout --quiet ${NAME1} && git pull
git checkout --quiet ${NAME2} && git pull

echo ""

TMPFILE="peb-$$.tmp"

git show-branch ${NAME1} ${NAME2} > ${TMPFILE}

COUNT1=`awk '/^--$/,EOF { print $0 }' "${TMPFILE}" | grep -E "( \* |\+  |\*  | \+ )\[${NAME1}([~^]|])" | wc -l`
COUNT2=`awk '/^--$/,EOF { print $0 }' "${TMPFILE}" | grep -E "( \* |\+  |\*  | \+ )\[${NAME2}([~^]|])" | wc -l`

rm "${TMPFILE}"

if [ ${COUNT1} -gt ${COUNT2} ]; then
  echo "Choosing '${NAME1}' (${COUNT1} unique commits, to ${COUNT2} on '${NAME2}')."
  git checkout ${NAME1}
elif [ ${COUNT2} -gt ${COUNT1} ]; then
  echo "Choosing '${NAME2}' (${COUNT2} unique commits, to ${COUNT1} on '${NAME1}')."
  git checkout ${NAME2}
else
  echo "Same: ${COUNT1} unique commits on both branches ('${NAME1}' and '${NAME2}')."
  echo "Choosing '${NAME1}'."
  git checkout ${NAME1}
fi