#!/bin/sh
# git-rebase-subtree - rebase "subtree of branches" in one go
# Copyright (C) 2007 Hans Ulrich Niedermann
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

unset CDPATH
SED="${SED-sed}"

self=`basename "$0"`
selfdir=`dirname "$0"`
selfdir=`cd "$selfdir" && pwd`
. "$selfdir/git-ndim-sh"

SUBDIRECTORY_OK="yes"
USAGE="<command> [params...]"

LONG_USAGE="\
Let a local subtree of branches follow a remote origin without too much merging.
For more details, see the ${self}(1) man page."
. git-sh-setup

require_work_tree

# Abort on error
set -e

#dry_run=:
dry_run=false

cmd() {
    echo "CMD>" "$@"
    "$dry_run" || "$@"
}


gf_init() {
    echo "$self: Examining configuration"
    config_found=no
    for configvar in "rebase-subtree.rebase" "rebase-subtree.subtree"
    do
        if test -n "$(git config --get-all "$configvar")"
        then
            if test "x$configvar" = "xrebase-subtree.subtree"; then
                echo "$self: WARNING: Using deprecated config variable rebase-subtree.subtree."
                echo "       Better use rebase-subtree.rebase lines instead."
            fi
            git config --get-all "$configvar" | while read from to restofline; do
                if test "x#" = "x$(echo "$from" | sed -n '1s/^\(.\).*/\1/p')"; then continue; fi
                echo ""
                echo "  From: $from"
                echo "    To: $to"
            done
            config_found=yes
            break
        fi
    done
    test "x$config_found" = "xyes" || die "Unset or empty git config var \"rebase-subtree.rebase\""
}

gf_branch() {
    branch="$1"
    newbranch="follow-old/$branch"
    if git rev-parse --verify "$branch" > /dev/null 2>&1; then
	# valid branch
	if git rev-parse --verify "$newbranch" > /dev/null 2>&1; then
	    : # branch already exists, do nothing
	else
	    cmd git branch "${newbranch}" "${branch}"
	fi
    else
	echo "$self: gf_branch called with invalid branch \"$branch\"" >&2
	exit 1
    fi
}


gf_rmbranch() {
    branch="$1"
    newbranch="follow-old/$branch"
    if git rev-parse --verify "$branch" > /dev/null 2>&1; then
	if git rev-parse --verify "$newbranch" > /dev/null 2>&1; then
	    cmd git-branch -D "${newbranch}"
	fi
    fi
}


gf_rebase_tree() {
    reverse="no"
    case "$1" in
	--reverse) reverse=yes; shift ;;
    esac
    newroot="$1"
    test "x$newroot" = "x" && die "Need <newroot> parameter"
    oldroot="$2"
    test "x$oldroot" = "x" && die "Need <oldroot> parameter"
    echo
    echo "CAUTION: ${self} does not handle merge errors yet - that will mess up your repo!"
    echo "Press Ctrl-C to abort. Or, if you feel adventurous, press ENTER."
    read
    echo
    echo "$self: Preparing subtree rebase"
    git config --get-all "$configvar" | while read from to restofline; do
	if test "x#" = "x$(echo "$from" | sed -n '1s/^\(.\).*/\1/p')"; then continue; fi
	gf_branch "$from"
	gf_branch "$to"
    done
    echo
    echo "$self: Executing subtree rebase"
    git config --get-all "$configvar" | while read from to restofline; do
	if test "x#" = "x$(echo "$from" | sed -n '1s/^\(.\).*/\1/p')"; then continue; fi
	if test "x$reverse" = "xno" && test "x$from" = "x$oldroot"; then
	    cmd git-rebase "$newroot" "$oldroot"
	    cmd git-rebase --onto "$newroot" "follow-old/$from" "$to"
	elif test "x$reverse" = "xyes" && test "x$from" = "x$newroot"; then
	    cmd git-rebase --onto "$newroot" "$oldroot" "$to"
	else
	    cmd git-rebase --onto "$from" "follow-old/$from" "$to"
	fi
    done
    echo
    echo "$self: Cleaning up after subtree rebase"
    git config --get-all "$configvar" | while read from to restofline; do
	if test "x#" = "x$(echo "$from" | sed -n '1s/^\(.\).*/\1/p')"; then continue; fi
	gf_rmbranch "$from"
	gf_rmbranch "$to"
    done
}

gf_init
gf_rebase_tree "$@"

# End of file.