#!/usr/bin/env python

# vim: et

from __future__ import with_statement

import os

import sys

import commands

import exceptions

def nearest_git_objects(path):

    dotgit = os.path.join(path, ".git")

    objects = os.path.join(path, "objects")

    if os.path.isdir(dotgit):

        return nearest_git_objects(dotgit)

    elif os.path.isdir(objects):

        return objects

    raise exceptions.RuntimeError("Could not find git dir from " + path)

def alt_path(git_path):

    return os.path.join(git_path, "info", "alternates")

def read_objs(git_path):

    fn = alt_path(git_path)

    alts = set()

    if os.path.exists(fn):

        with open(fn) as f:

            alts = set([l.strip() for l in f.readlines()])

    return alts

def setup_alternates(from_objects, to_objects):

    alts = read_objs(from_objects)

    alts.add(to_objects)

    with open(alt_path(from_objects), "w") as f:

        f.write("\n".join(alts) + "\n")

def here():

    (e, o) = commands.getstatusoutput("git rev-parse --git-dir")

    if e != 0:

        raise exceptions.RuntimeError("This is not a git repo.")

    return nearest_git_objects(o.strip())

def setup_new_alternate(where):

    alt = nearest_git_objects(where)

    loc = here()

    print loc, "->", alt

    setup_alternates(loc, alt)

def display_alternates():

    p = here()

    alts = read_objs(p)

    print "Alternates for %s (%d):" % (p, len(alts))

    for s in sorted(alts):

        print "   %s" % s

if __name__ == '__main__':

    if len(sys.argv) < 2:

        display_alternates()

    else:

        setup_new_alternate(sys.argv[1])