Diff working-tree of two git repositories, testing multiple branches

diff-repos.sh

#! /usr/bin/env bash

_V="0.0.1"

function print_usage() {
  printf '=%.0s' {1..80}; printf '\n'
  echo "Diff Repos - $_V"
  echo "Diff working-tree of two git repositories, testing multiple branches"
  echo "Depends: ./diff-branches, write-access to ./"
  echo "Usage: ./diff-repos.sh <repository_1> <repository_2> [-v]"
  echo "  -v | verbose; print diff log to stdout"
  exit 1;
}

# branches to compare are stored in a
# simple text file ./diff-branches
#  - one branch per line
if [ ! -e ./diff-branches ]; then
  echo "No branch list (./diff-branches) found!"
  exit 1;
fi

# show error when given path isn't a git repository
function no_repo_report() {
  echo "No git repository found at: $1/.git"
  echo "Notice: This script doesn't work with --bare repositories."
}

# eye candy
function print_header() {
  printf '=%.0s' {1..80}; printf '\n'
  echo "Comparing branch: $1"
  printf '=%.0s' {1..80}; printf '\n'
}
function print_footer() {
  printf '~%.0s' {1..80}; printf '\n'
  echo "Differences: $1 "
  printf '=%.0s' {1..80}; printf '\n'
  printf '\n\n'
}

# set up repository paths
_REPO_1=$1
if [ ! -e "$_REPO_1/.git" ]; then
  no_repo_report $_REPO_1
  print_usage
  exit 1;
fi
_REPO_2=$2
if [ ! -e "$_REPO_2/.git" ]; then
  no_repo_report $_REPO_2
  print_usage
  exit 1;
fi

# changes branches within both
# given repositories
function change_branch() {
  echo -n "Entering $1 >> "
  cd $1
  echo -n "Checking out $2 >> "
  git checkout $2
  echo "Returning to parent."
  cd ..
}

echo -e "Processing ./diff-branches:\n"
# main loop
while read branch; do
  # skip empty lines
  if [ "$branch" == "" ]; then
    echo "Skipping empty line..."
    continue
  fi

  # new log entry
  print_header $branch
  # change branches in repos
  change_branch $_REPO_1 $branch
  change_branch $_REPO_2 $branch
  # diff both repos,
  #  -q: only showing differences
  #  -r: recursively,
  #  -x: ignoring .git folder (obviously different; it's the point of it all)
  diff_log=./.diff-log-$branch
  diff $_REPO_1 $_REPO_2 -qr -x .git &> $diff_log
  [ "$3" == "-v" ] && cat $diff_log
  print_footer `cat $diff_log | wc -l`

done < ./diff-branches