#! /bin/sh
set -e

### Huh?
###
### This script is an adaptor for git mergetool so that, while /it/ thinks
### it's using emerge, it's really using ediff, which is much better, and
### maybe a long-running Emacs via gnuserv.

## Find out what we're supposed to be doing.  The command line looks like
##
## emerge-hack -f emerge-mumble FILE FILE ... OUTPUT

dashf=$1
command=$2
shift 2
case "$dashf" in
  -f) ;;
  *) echo >&2 "$0: expected -f emerge-mumble"; exit 1;;
esac

case "$command" in
  emerge-files-with-ancestor-command)
    func=ediff-merge-files-with-ancestor
    ;;
  emerge-merge-files-command)
    func=ediff-files
    ;;
  *)
    echo >&2 "$0: unexpected command $command"
    exit 1
    ;;
esac

## Find out whether there's a plausible-looking gnuserv.

if gnuclient -batch -eval t >/dev/null 2>&1; then
  emacs="gnuclient"
else
  emacs="emacs"
fi

## Now build the command line.
##
## The hairy-looking seddery is there to quotify file names properly for
## Lisp.  We also need to make sure that the filenames are absolute.
## Finally, there's a little tweak to separate off the last name because of
## the strange argument order ediff uses.

expr=""
sep=""
last="$func"

for i; do
  name=$i
  case "$name" in
    /*);;
    *) name=`pwd`/$name;;
  esac
  quot=$(echo -n "$name" |
    sed -n '
    1 h
    2,$ H
    $ {
      g
      s/["\\]/\\&/
      s/^/"/
      s/$/"/
      s/\
/\\n/
      p
    }
')
  expr="$expr$sep$last"
  sep=" "
  last=$quot
  output=$name
done

## Done.  Note that we pass the output filename again, as an explicit
## argument.  This will make gnuclient wait until we've finished with the
## merge.

exec "$emacs" -eval "($expr${sep}nil $last)" "$output"