bin/git-vee

#!/bin/sh
#
# This prepares a brief summary of how your current branch has diverged 
# from a corresponding remote branch.  A typical use is:
#   git vee origin
#
# if the currently-checked-out branch is master, this will compare
# master and origin/master.  
#
# It uses git log --cherry-mark, so you need at least git 1.7.4.1.
# If --cherry-mark doesn't work, delete that option from this script.
#
# Usage:
#   git vee # compare current head branch and its remote tracking branch
#   git vee remote  # compare current head branch and its analog on the remote
#   git vee remote branch # compare branch and remote/branch
#   git vee branch  # compare HEAD and branch
#   git vee branch1 branch2 # compare branch1 and branch2
#

DIE=false;

equal_commits () {
  [ $(git rev-parse $A) = $(git rev-parse $B) ]
}  

valid_ref () {
  git rev-parse -q --verify $1 >/dev/null
}

is_remote () {
  git remote | grep -q "^$1"'$'
}

die_later () {
  echo $* 1>&2;
  DIE=true
}

die_now () {
  $DIE && exit 1
}

die () {
  echo 1>&2 "$@"
  exit 1
}

usage () {
  echo "Usage: $0 [remote] [branch]" 1>&2
  echo "       $0 branch-a [branch-b]" 1>&2
  exit 2
}

print_command_only=false
case $1 in
    -q) print_command_only=true; shift ;;
esac

case $# in
  0) Y=$(git get current-branch-name);
     [ -z "$Y" ] && die "Couldn't get current branch name"
     B=$(git get branch-tracked-branch $Y);
     if [ -z "$B" ] ; then
         X=$(git get branch-tracked-branch $Y);
         [ -z "$X" ] && die "Couldn't find remote tracking branch for '$Y'"
     fi
     ;;
  1) X=$1 Y=HEAD;;
  2) X=$1 Y=$2;;
  *) usage ;;
esac

if [ -n "$B" ]; then
    A=$Y
elif is_remote $X; then
  if [ $Y = HEAD ]; then
      Y=$(git get current-branch-name)
  fi
  A=$Y B="$X/$Y"
else 
  A=$X; B=$Y;
fi

valid_ref $A || die_later "$A: unknown commit"
valid_ref $B || die_later "$B: unknown commit"
die_now

if equal_commits $A $B ; then
  echo "$A and $B are identical"
  exit 0;
fi

cmd="git log --decorate --cherry-mark --oneline --graph --boundary $A...$B"
if $print_command_only; then
    echo $cmd
else
    $cmd
fi