#!/bin/bash
set -e

# stg-whatchanged - show a metadiff for the patch being modified,
# especially when resolving a merge.

# Copyright (c) 2006-2007 Yann Dirson <ydirson@altern.org>
# Subject to the GNU GPL, version 2.

# FIXME:
# - should only exclude hunk headers differing only in line offsets
# - diff coloring should show changes in context lines differently than
#   changes in contents
# - filter on ^index lines is a bit wide
# - we should be able to ask diff to force a new hunk on "^@@ " to better
#   handle them
# - we should always show the hunk header for any changes within a hunk

# default to unified diff
if [ "$#" = 0 ]; then
    set -- -u
fi

# Merges via "push" leave top=bottom so we must look at old patch
# in this case (unlike, eg., "pick --fold")
patchdir="$(git-rev-parse --git-dir)/patches/$(stg branch)/$(stg top)"
if [ $(cat "$patchdir/bottom") = $(cat "$patchdir/top") ];
then
    current_cmd="stg show //top.old"
else
    current_cmd="stg show"
fi

colordiff "$@" \
    -I '^index [0-9a-b]*..[0-9a-b]*' \
    -I '^@@ .* @@' \
    <($current_cmd) <(stg diff -r//bottom) | less -RFX