# porcelain.py -- Porcelain-like layer on top of Dulwich
# Copyright (C) 2013 Jelmer Vernooij <jelmer@jelmer.uk>
#
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as public by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#

"""Simple wrapper that provides porcelain-like functions on top of Dulwich.

Currently implemented:
 * archive
 * add
 * branch{_create,_delete,_list}
 * check-ignore
 * checkout
 * clone
 * commit
 * commit-tree
 * daemon
 * describe
 * diff-tree
 * fetch
 * init
 * ls-files
 * ls-remote
 * ls-tree
 * pull
 * push
 * rm
 * remote{_add}
 * receive-pack
 * reset
 * rev-list
 * tag{_create,_delete,_list}
 * upload-pack
 * update-server-info
 * status
 * symbolic-ref

These functions are meant to behave similarly to the git subcommands.
Differences in behaviour are considered bugs.

Functions should generally accept both unicode strings and bytestrings
"""

from collections import namedtuple
from contextlib import (
    closing,
    contextmanager,
)
from io import BytesIO, RawIOBase
import datetime
import os
import posixpath
import stat
import sys
import time

from dulwich.archive import (
    tar_stream,
    )
from dulwich.client import (
    get_transport_and_path,
    )
from dulwich.config import (
    StackedConfig,
    )
from dulwich.diff_tree import (
    CHANGE_ADD,
    CHANGE_DELETE,
    CHANGE_MODIFY,
    CHANGE_RENAME,
    CHANGE_COPY,
    RENAME_CHANGE_TYPES,
    )
from dulwich.errors import (
    SendPackError,
    UpdateRefsError,
    )
from dulwich.ignore import IgnoreFilterManager
from dulwich.index import (
    blob_from_path_and_stat,
    get_unstaged_changes,
    )
from dulwich.object_store import (
    tree_lookup_path,
    )
from dulwich.objects import (
    Commit,
    Tag,
    format_timezone,
    parse_timezone,
    pretty_format_tree_entry,
    )
from dulwich.objectspec import (
    parse_commit,
    parse_object,
    parse_ref,
    parse_reftuples,
    parse_tree,
    )
from dulwich.pack import (
    write_pack_index,
    write_pack_objects,
    )
from dulwich.patch import write_tree_diff
from dulwich.protocol import (
    Protocol,
    ZERO_SHA,
    )
from dulwich.refs import (
    ANNOTATED_TAG_SUFFIX,
    strip_peeled_refs,
)
from dulwich.repo import (BaseRepo, Repo)
from dulwich.server import (
    FileSystemBackend,
    TCPGitServer,
    ReceivePackHandler,
    UploadPackHandler,
    update_server_info as server_update_server_info,
    )


# Module level tuple definition for status output
GitStatus = namedtuple('GitStatus', 'staged unstaged untracked')


class NoneStream(RawIOBase):
    """Fallback if stdout or stderr are unavailable, does nothing."""
    def read(self, size=-1):
        return None

    def readall(self):
        return None

    def readinto(self, b):
        return None

    def write(self, b):
        return None


if sys.version_info[0] == 2:
    default_bytes_out_stream = sys.stdout or NoneStream()
    default_bytes_err_stream = sys.stderr or NoneStream()
else:
    default_bytes_out_stream = (
        getattr(sys.stdout, 'buffer', None) or NoneStream())
    default_bytes_err_stream = (
        getattr(sys.stderr, 'buffer', None) or NoneStream())


DEFAULT_ENCODING = 'utf-8'


class RemoteExists(Exception):
    """Raised when the remote already exists."""


def open_repo(path_or_repo):
    """Open an argument that can be a repository or a path for a repository."""
    if isinstance(path_or_repo, BaseRepo):
        return path_or_repo
    return Repo(path_or_repo)


@contextmanager
def _noop_context_manager(obj):
    """Context manager that has the same api as closing but does nothing."""
    yield obj


def open_repo_closing(path_or_repo):
    """Open an argument that can be a repository or a path for a repository.
    returns a context manager that will close the repo on exit if the argument
    is a path, else does nothing if the argument is a repo.
    """
    if isinstance(path_or_repo, BaseRepo):
        return _noop_context_manager(path_or_repo)
    return closing(Repo(path_or_repo))


def path_to_tree_path(repopath, path):
    """Convert a path to a path usable in an index, e.g. bytes and relative to
    the repository root.

    :param repopath: Repository path, absolute or relative to the cwd
    :param path: A path, absolute or relative to the cwd
    :return: A path formatted for use in e.g. an index
    """
    if not isinstance(path, bytes):
        path = path.encode(sys.getfilesystemencoding())
    if not isinstance(repopath, bytes):
        repopath = repopath.encode(sys.getfilesystemencoding())
    treepath = os.path.relpath(path, repopath)
    if treepath.startswith(b'..'):
        raise ValueError('Path not in repo')
    if os.path.sep != '/':
        treepath = treepath.replace(os.path.sep.encode('ascii'), b'/')
    return treepath


def archive(repo, committish=None, outstream=default_bytes_out_stream,
            errstream=default_bytes_err_stream):
    """Create an archive.

    :param repo: Path of repository for which to generate an archive.
    :param committish: Commit SHA1 or ref to use
    :param outstream: Output stream (defaults to stdout)
    :param errstream: Error stream (defaults to stderr)
    """

    if committish is None:
        committish = "HEAD"
    with open_repo_closing(repo) as repo_obj:
        c = parse_commit(repo_obj, committish)
        for chunk in tar_stream(
                repo_obj.object_store, repo_obj.object_store[c.tree],
                c.commit_time):
            outstream.write(chunk)


def update_server_info(repo="."):
    """Update server info files for a repository.

    :param repo: path to the repository
    """
    with open_repo_closing(repo) as r:
        server_update_server_info(r)


def symbolic_ref(repo, ref_name, force=False):
    """Set git symbolic ref into HEAD.

    :param repo: path to the repository
    :param ref_name: short name of the new ref
    :param force: force settings without checking if it exists in refs/heads
    """
    with open_repo_closing(repo) as repo_obj:
        ref_path = _make_branch_ref(ref_name)
        if not force and ref_path not in repo_obj.refs.keys():
            raise ValueError('fatal: ref `%s` is not a ref' % ref_name)
        repo_obj.refs.set_symbolic_ref(b'HEAD', ref_path)


def commit(repo=".", message=None, author=None, committer=None, encoding=None):
    """Create a new commit.

    :param repo: Path to repository
    :param message: Optional commit message
    :param author: Optional author name and email
    :param committer: Optional committer name and email
    :return: SHA1 of the new commit
    """
    # FIXME: Support --all argument
    # FIXME: Support --signoff argument
    if getattr(message, 'encode', None):
        message = message.encode(encoding or DEFAULT_ENCODING)
    if getattr(author, 'encode', None):
        author = author.encode(encoding or DEFAULT_ENCODING)
    if getattr(committer, 'encode', None):
        committer = committer.encode(encoding or DEFAULT_ENCODING)
    with open_repo_closing(repo) as r:
        return r.do_commit(
                message=message, author=author, committer=committer,
                encoding=encoding)


def commit_tree(repo, tree, message=None, author=None, committer=None):
    """Create a new commit object.

    :param repo: Path to repository
    :param tree: An existing tree object
    :param author: Optional author name and email
    :param committer: Optional committer name and email
    """
    with open_repo_closing(repo) as r:
        return r.do_commit(
            message=message, tree=tree, committer=committer, author=author)


def init(path=".", bare=False):
    """Create a new git repository.

    :param path: Path to repository.
    :param bare: Whether to create a bare repository.
    :return: A Repo instance
    """
    if not os.path.exists(path):
        os.mkdir(path)

    if bare:
        return Repo.init_bare(path)
    else:
        return Repo.init(path)


def clone(source, target=None, bare=False, checkout=None,
          errstream=default_bytes_err_stream, outstream=None,
          origin=b"origin", depth=None, **kwargs):
    """Clone a local or remote git repository.

    :param source: Path or URL for source repository
    :param target: Path to target repository (optional)
    :param bare: Whether or not to create a bare repository
    :param checkout: Whether or not to check-out HEAD after cloning
    :param errstream: Optional stream to write progress to
    :param outstream: Optional stream to write progress to (deprecated)
    :param origin: Name of remote from the repository used to clone
    :param depth: Depth to fetch at
    :return: The new repository
    """
    # TODO(user): This code overlaps quite a bit with Repo.clone
    if outstream is not None:
        import warnings
        warnings.warn(
            "outstream= has been deprecated in favour of errstream=.",
            DeprecationWarning, stacklevel=3)
        errstream = outstream

    if checkout is None:
        checkout = (not bare)
    if checkout and bare:
        raise ValueError("checkout and bare are incompatible")

    if target is None:
        target = source.split("/")[-1]

    if not os.path.exists(target):
        os.mkdir(target)

    if bare:
        r = Repo.init_bare(target)
    else:
        r = Repo.init(target)

    reflog_message = b'clone: from ' + source.encode('utf-8')
    try:
        fetch_result = fetch(
            r, source, origin, errstream=errstream, message=reflog_message,
            depth=depth, **kwargs)
        target_config = r.get_config()
        if not isinstance(source, bytes):
            source = source.encode(DEFAULT_ENCODING)
        target_config.set((b'remote', origin), b'url', source)
        target_config.set(
            (b'remote', origin), b'fetch',
            b'+refs/heads/*:refs/remotes/' + origin + b'/*')
        target_config.write_to_path()
        # TODO(user): Support symref capability,
        # https://github.com/jelmer/dulwich/issues/485
        try:
            head = r[fetch_result[b'HEAD']]
        except KeyError:
            head = None
        else:
            r[b'HEAD'] = head.id
        if checkout and not bare and head is not None:
            errstream.write(b'Checking out ' + head.id + b'\n')
            r.reset_index(head.tree)
    except BaseException:
        r.close()
        raise

    return r


def add(repo=".", paths=None):
    """Add files to the staging area.

    :param repo: Repository for the files
    :param paths: Paths to add.  No value passed stages all modified files.
    :return: Tuple with set of added files and ignored files
    """
    ignored = set()
    with open_repo_closing(repo) as r:
        ignore_manager = IgnoreFilterManager.from_repo(r)
        if not paths:
            paths = list(
                get_untracked_paths(os.getcwd(), r.path, r.open_index()))
        relpaths = []
        if not isinstance(paths, list):
            paths = [paths]
        for p in paths:
            relpath = os.path.relpath(p, r.path)
            if relpath.startswith('..' + os.path.sep):
                raise ValueError('path %r is not in repo' % relpath)
            # FIXME: Support patterns, directories.
            if ignore_manager.is_ignored(relpath):
                ignored.add(relpath)
                continue
            relpaths.append(relpath)
        r.stage(relpaths)
    return (relpaths, ignored)


def remove(repo=".", paths=None, cached=False):
    """Remove files from the staging area.

    :param repo: Repository for the files
    :param paths: Paths to remove
    """
    with open_repo_closing(repo) as r:
        index = r.open_index()
        for p in paths:
            full_path = os.path.abspath(p).encode(sys.getfilesystemencoding())
            tree_path = path_to_tree_path(r.path, p)
            try:
                index_sha = index[tree_path].sha
            except KeyError:
                raise Exception('%s did not match any files' % p)

            if not cached:
                try:
                    st = os.lstat(full_path)
                except OSError:
                    pass
                else:
                    try:
                        blob = blob_from_path_and_stat(full_path, st)
                    except IOError:
                        pass
                    else:
                        try:
                            committed_sha = tree_lookup_path(
                                r.__getitem__, r[r.head()].tree, tree_path)[1]
                        except KeyError:
                            committed_sha = None

                        if blob.id != index_sha and index_sha != committed_sha:
                            raise Exception(
                                'file has staged content differing '
                                'from both the file and head: %s' % p)

                        if index_sha != committed_sha:
                            raise Exception(
                                'file has staged changes: %s' % p)
                        os.remove(full_path)
            del index[tree_path]
        index.write()


rm = remove


def commit_decode(commit, contents, default_encoding=DEFAULT_ENCODING):
    if commit.encoding is not None:
        return contents.decode(commit.encoding, "replace")
    return contents.decode(default_encoding, "replace")


def print_commit(commit, decode, outstream=sys.stdout):
    """Write a human-readable commit log entry.

    :param commit: A `Commit` object
    :param outstream: A stream file to write to
    """
    outstream.write("-" * 50 + "\n")
    outstream.write("commit: " + commit.id.decode('ascii') + "\n")
    if len(commit.parents) > 1:
        outstream.write(
            "merge: " +
            "...".join([c.decode('ascii') for c in commit.parents[1:]]) + "\n")
    outstream.write("Author: " + decode(commit.author) + "\n")
    if commit.author != commit.committer:
        outstream.write("Committer: " + decode(commit.committer) + "\n")

    time_tuple = time.gmtime(commit.author_time + commit.author_timezone)
    time_str = time.strftime("%a %b %d %Y %H:%M:%S", time_tuple)
    timezone_str = format_timezone(commit.author_timezone).decode('ascii')
    outstream.write("Date:   " + time_str + " " + timezone_str + "\n")
    outstream.write("\n")
    outstream.write(decode(commit.message) + "\n")
    outstream.write("\n")


def print_tag(tag, decode, outstream=sys.stdout):
    """Write a human-readable tag.

    :param tag: A `Tag` object
    :param decode: Function for decoding bytes to unicode string
    :param outstream: A stream to write to
    """
    outstream.write("Tagger: " + decode(tag.tagger) + "\n")
    outstream.write("Date:   " + decode(tag.tag_time) + "\n")
    outstream.write("\n")
    outstream.write(decode(tag.message) + "\n")
    outstream.write("\n")


def show_blob(repo, blob, decode, outstream=sys.stdout):
    """Write a blob to a stream.

    :param repo: A `Repo` object
    :param blob: A `Blob` object
    :param decode: Function for decoding bytes to unicode string
    :param outstream: A stream file to write to
    """
    outstream.write(decode(blob.data))


def show_commit(repo, commit, decode, outstream=sys.stdout):
    """Show a commit to a stream.

    :param repo: A `Repo` object
    :param commit: A `Commit` object
    :param decode: Function for decoding bytes to unicode string
    :param outstream: Stream to write to
    """
    print_commit(commit, decode=decode, outstream=outstream)
    if commit.parents:
        parent_commit = repo[commit.parents[0]]
        base_tree = parent_commit.tree
    else:
        base_tree = None
    diffstream = BytesIO()
    write_tree_diff(
        diffstream,
        repo.object_store, base_tree, commit.tree)
    diffstream.seek(0)
    outstream.write(
        diffstream.getvalue().decode(
                commit.encoding or DEFAULT_ENCODING, 'replace'))


def show_tree(repo, tree, decode, outstream=sys.stdout):
    """Print a tree to a stream.

    :param repo: A `Repo` object
    :param tree: A `Tree` object
    :param decode: Function for decoding bytes to unicode string
    :param outstream: Stream to write to
    """
    for n in tree:
        outstream.write(decode(n) + "\n")


def show_tag(repo, tag, decode, outstream=sys.stdout):
    """Print a tag to a stream.

    :param repo: A `Repo` object
    :param tag: A `Tag` object
    :param decode: Function for decoding bytes to unicode string
    :param outstream: Stream to write to
    """
    print_tag(tag, decode, outstream)
    show_object(repo, repo[tag.object[1]], outstream)


def show_object(repo, obj, decode, outstream):
    return {
        b"tree": show_tree,
        b"blob": show_blob,
        b"commit": show_commit,
        b"tag": show_tag,
            }[obj.type_name](repo, obj, decode, outstream)


def print_name_status(changes):
    """Print a simple status summary, listing changed files.
    """
    for change in changes:
        if not change:
            continue
        if isinstance(change, list):
            change = change[0]
        if change.type == CHANGE_ADD:
            path1 = change.new.path
            path2 = ''
            kind = 'A'
        elif change.type == CHANGE_DELETE:
            path1 = change.old.path
            path2 = ''
            kind = 'D'
        elif change.type == CHANGE_MODIFY:
            path1 = change.new.path
            path2 = ''
            kind = 'M'
        elif change.type in RENAME_CHANGE_TYPES:
            path1 = change.old.path
            path2 = change.new.path
            if change.type == CHANGE_RENAME:
                kind = 'R'
            elif change.type == CHANGE_COPY:
                kind = 'C'
        yield '%-8s%-20s%-20s' % (kind, path1, path2)


def log(repo=".", paths=None, outstream=sys.stdout, max_entries=None,
        reverse=False, name_status=False):
    """Write commit logs.

    :param repo: Path to repository
    :param paths: Optional set of specific paths to print entries for
    :param outstream: Stream to write log output to
    :param reverse: Reverse order in which entries are printed
    :param name_status: Print name status
    :param max_entries: Optional maximum number of entries to display
    """
    with open_repo_closing(repo) as r:
        walker = r.get_walker(
            max_entries=max_entries, paths=paths, reverse=reverse)
        for entry in walker:
            def decode(x):
                return commit_decode(entry.commit, x)
            print_commit(entry.commit, decode, outstream)
            if name_status:
                outstream.writelines(
                    [l+'\n' for l in print_name_status(entry.changes())])


# TODO(user): better default for encoding?
def show(repo=".", objects=None, outstream=sys.stdout,
         default_encoding=DEFAULT_ENCODING):
    """Print the changes in a commit.

    :param repo: Path to repository
    :param objects: Objects to show (defaults to [HEAD])
    :param outstream: Stream to write to
    :param default_encoding: Default encoding to use if none is set in the
        commit
    """
    if objects is None:
        objects = ["HEAD"]
    if not isinstance(objects, list):
        objects = [objects]
    with open_repo_closing(repo) as r:
        for objectish in objects:
            o = parse_object(r, objectish)
            if isinstance(o, Commit):
                def decode(x):
                    return commit_decode(o, x, default_encoding)
            else:
                def decode(x):
                    return x.decode(default_encoding)
            show_object(r, o, decode, outstream)


def diff_tree(repo, old_tree, new_tree, outstream=sys.stdout):
    """Compares the content and mode of blobs found via two tree objects.

    :param repo: Path to repository
    :param old_tree: Id of old tree
    :param new_tree: Id of new tree
    :param outstream: Stream to write to
    """
    with open_repo_closing(repo) as r:
        write_tree_diff(outstream, r.object_store, old_tree, new_tree)


def rev_list(repo, commits, outstream=sys.stdout):
    """Lists commit objects in reverse chronological order.

    :param repo: Path to repository
    :param commits: Commits over which to iterate
    :param outstream: Stream to write to
    """
    with open_repo_closing(repo) as r:
        for entry in r.get_walker(include=[r[c].id for c in commits]):
            outstream.write(entry.commit.id + b"\n")


def tag(*args, **kwargs):
    import warnings
    warnings.warn("tag has been deprecated in favour of tag_create.",
                  DeprecationWarning)
    return tag_create(*args, **kwargs)


def tag_create(
        repo, tag, author=None, message=None, annotated=False,
        objectish="HEAD", tag_time=None, tag_timezone=None,
        sign=False):
    """Creates a tag in git via dulwich calls:

    :param repo: Path to repository
    :param tag: tag string
    :param author: tag author (optional, if annotated is set)
    :param message: tag message (optional)
    :param annotated: whether to create an annotated tag
    :param objectish: object the tag should point at, defaults to HEAD
    :param tag_time: Optional time for annotated tag
    :param tag_timezone: Optional timezone for annotated tag
    :param sign: GPG Sign the tag
    """

    with open_repo_closing(repo) as r:
        object = parse_object(r, objectish)

        if annotated:
            # Create the tag object
            tag_obj = Tag()
            if author is None:
                # TODO(user): Don't use repo private method.
                author = r._get_user_identity(r.get_config_stack())
            tag_obj.tagger = author
            tag_obj.message = message
            tag_obj.name = tag
            tag_obj.object = (type(object), object.id)
            if tag_time is None:
                tag_time = int(time.time())
            tag_obj.tag_time = tag_time
            if tag_timezone is None:
                # TODO(user) Use current user timezone rather than UTC
                tag_timezone = 0
            elif isinstance(tag_timezone, str):
                tag_timezone = parse_timezone(tag_timezone)
            tag_obj.tag_timezone = tag_timezone
            if sign:
                import gpg
                with gpg.Context(armor=True) as c:
                    tag_obj.signature, result = c.sign(tag_obj.as_raw_string())
            r.object_store.add_object(tag_obj)
            tag_id = tag_obj.id
        else:
            tag_id = object.id

        r.refs[_make_tag_ref(tag)] = tag_id


def list_tags(*args, **kwargs):
    import warnings
    warnings.warn("list_tags has been deprecated in favour of tag_list.",
                  DeprecationWarning)
    return tag_list(*args, **kwargs)


def tag_list(repo, outstream=sys.stdout):
    """List all tags.

    :param repo: Path to repository
    :param outstream: Stream to write tags to
    """
    with open_repo_closing(repo) as r:
        tags = sorted(r.refs.as_dict(b"refs/tags"))
        return tags


def tag_delete(repo, name):
    """Remove a tag.

    :param repo: Path to repository
    :param name: Name of tag to remove
    """
    with open_repo_closing(repo) as r:
        if isinstance(name, bytes):
            names = [name]
        elif isinstance(name, list):
            names = name
        else:
            raise TypeError("Unexpected tag name type %r" % name)
        for name in names:
            del r.refs[_make_tag_ref(name)]


def reset(repo, mode, treeish="HEAD"):
    """Reset current HEAD to the specified state.

    :param repo: Path to repository
    :param mode: Mode ("hard", "soft", "mixed")
    :param treeish: Treeish to reset to
    """

    if mode != "hard":
        raise ValueError("hard is the only mode currently supported")

    with open_repo_closing(repo) as r:
        tree = parse_tree(r, treeish)
        r.reset_index(tree.id)


def push(repo, remote_location, refspecs,
         outstream=default_bytes_out_stream,
         errstream=default_bytes_err_stream, **kwargs):
    """Remote push with dulwich via dulwich.client

    :param repo: Path to repository
    :param remote_location: Location of the remote
    :param refspecs: Refs to push to remote
    :param outstream: A stream file to write output
    :param errstream: A stream file to write errors
    """

    # Open the repo
    with open_repo_closing(repo) as r:

        # Get the client and path
        client, path = get_transport_and_path(
                remote_location, config=r.get_config_stack(), **kwargs)

        selected_refs = []

        def update_refs(refs):
            selected_refs.extend(parse_reftuples(r.refs, refs, refspecs))
            new_refs = {}
            # TODO: Handle selected_refs == {None: None}
            for (lh, rh, force) in selected_refs:
                if lh is None:
                    new_refs[rh] = ZERO_SHA
                else:
                    new_refs[rh] = r.refs[lh]
            return new_refs

        err_encoding = getattr(errstream, 'encoding', None) or DEFAULT_ENCODING
        remote_location_bytes = client.get_url(path).encode(err_encoding)
        try:
            client.send_pack(
                path, update_refs,
                generate_pack_data=r.object_store.generate_pack_data,
                progress=errstream.write)
            errstream.write(
                b"Push to " + remote_location_bytes + b" successful.\n")
        except (UpdateRefsError, SendPackError) as e:
            errstream.write(b"Push to " + remote_location_bytes +
                            b" failed -> " + e.message.encode(err_encoding) +
                            b"\n")


def pull(repo, remote_location=None, refspecs=None,
         outstream=default_bytes_out_stream,
         errstream=default_bytes_err_stream, **kwargs):
    """Pull from remote via dulwich.client

    :param repo: Path to repository
    :param remote_location: Location of the remote
    :param refspec: refspecs to fetch
    :param outstream: A stream file to write to output
    :param errstream: A stream file to write to errors
    """
    # Open the repo
    with open_repo_closing(repo) as r:
        if remote_location is None:
            # TODO(user): Lookup 'remote' for current branch in config
            raise NotImplementedError(
                "looking up remote from branch config not supported yet")
        if refspecs is None:
            refspecs = [b"HEAD"]
        selected_refs = []

        def determine_wants(remote_refs):
            selected_refs.extend(
                parse_reftuples(remote_refs, r.refs, refspecs))
            return [remote_refs[lh] for (lh, rh, force) in selected_refs]
        client, path = get_transport_and_path(
                remote_location, config=r.get_config_stack(), **kwargs)
        fetch_result = client.fetch(
            path, r, progress=errstream.write, determine_wants=determine_wants)
        for (lh, rh, force) in selected_refs:
            r.refs[rh] = fetch_result.refs[lh]
        if selected_refs:
            r[b'HEAD'] = fetch_result.refs[selected_refs[0][1]]

        # Perform 'git checkout .' - syncs staged changes
        tree = r[b"HEAD"].tree
        r.reset_index(tree=tree)


def status(repo=".", ignored=False):
    """Returns staged, unstaged, and untracked changes relative to the HEAD.

    :param repo: Path to repository or repository object
    :param ignored: Whether to include ignored files in `untracked`
    :return: GitStatus tuple,
        staged -    list of staged paths (diff index/HEAD)
        unstaged -  list of unstaged paths (diff index/working-tree)
        untracked - list of untracked, un-ignored & non-.git paths
    """
    with open_repo_closing(repo) as r:
        # 1. Get status of staged
        tracked_changes = get_tree_changes(r)
        # 2. Get status of unstaged
        index = r.open_index()
        normalizer = r.get_blob_normalizer()
        filter_callback = normalizer.checkin_normalize
        unstaged_changes = list(
            get_unstaged_changes(index, r.path, filter_callback)
        )
        ignore_manager = IgnoreFilterManager.from_repo(r)
        untracked_paths = get_untracked_paths(r.path, r.path, index)
        if ignored:
            untracked_changes = list(untracked_paths)
        else:
            untracked_changes = [
                    p for p in untracked_paths
                    if not ignore_manager.is_ignored(p)]
        return GitStatus(tracked_changes, unstaged_changes, untracked_changes)


def get_untracked_paths(frompath, basepath, index):
    """Get untracked paths.

    ;param frompath: Path to walk
    :param basepath: Path to compare to
    :param index: Index to check against
    """
    # If nothing is specified, add all non-ignored files.
    for dirpath, dirnames, filenames in os.walk(frompath):
        # Skip .git and below.
        if '.git' in dirnames:
            dirnames.remove('.git')
            if dirpath != basepath:
                continue
        if '.git' in filenames:
            filenames.remove('.git')
            if dirpath != basepath:
                continue
        for filename in filenames:
            ap = os.path.join(dirpath, filename)
            ip = path_to_tree_path(basepath, ap)
            if ip not in index:
                yield os.path.relpath(ap, frompath)


def get_tree_changes(repo):
    """Return add/delete/modify changes to tree by comparing index to HEAD.

    :param repo: repo path or object
    :return: dict with lists for each type of change
    """
    with open_repo_closing(repo) as r:
        index = r.open_index()

        # Compares the Index to the HEAD & determines changes
        # Iterate through the changes and report add/delete/modify
        # TODO: call out to dulwich.diff_tree somehow.
        tracked_changes = {
            'add': [],
            'delete': [],
            'modify': [],
        }
        try:
            tree_id = r[b'HEAD'].tree
        except KeyError:
            tree_id = None

        for change in index.changes_from_tree(r.object_store, tree_id):
            if not change[0][0]:
                tracked_changes['add'].append(change[0][1])
            elif not change[0][1]:
                tracked_changes['delete'].append(change[0][0])
            elif change[0][0] == change[0][1]:
                tracked_changes['modify'].append(change[0][0])
            else:
                raise AssertionError('git mv ops not yet supported')
        return tracked_changes


def daemon(path=".", address=None, port=None):
    """Run a daemon serving Git requests over TCP/IP.

    :param path: Path to the directory to serve.
    :param address: Optional address to listen on (defaults to ::)
    :param port: Optional port to listen on (defaults to TCP_GIT_PORT)
    """
    # TODO(user): Support git-daemon-export-ok and --export-all.
    backend = FileSystemBackend(path)
    server = TCPGitServer(backend, address, port)
    server.serve_forever()


def web_daemon(path=".", address=None, port=None):
    """Run a daemon serving Git requests over HTTP.

    :param path: Path to the directory to serve
    :param address: Optional address to listen on (defaults to ::)
    :param port: Optional port to listen on (defaults to 80)
    """
    from dulwich.web import (
        make_wsgi_chain,
        make_server,
        WSGIRequestHandlerLogger,
        WSGIServerLogger)

    backend = FileSystemBackend(path)
    app = make_wsgi_chain(backend)
    server = make_server(address, port, app,
                         handler_class=WSGIRequestHandlerLogger,
                         server_class=WSGIServerLogger)
    server.serve_forever()


def upload_pack(path=".", inf=None, outf=None):
    """Upload a pack file after negotiating its contents using smart protocol.

    :param path: Path to the repository
    :param inf: Input stream to communicate with client
    :param outf: Output stream to communicate with client
    """
    if outf is None:
        outf = getattr(sys.stdout, 'buffer', sys.stdout)
    if inf is None:
        inf = getattr(sys.stdin, 'buffer', sys.stdin)
    path = os.path.expanduser(path)
    backend = FileSystemBackend(path)

    def send_fn(data):
        outf.write(data)
        outf.flush()
    proto = Protocol(inf.read, send_fn)
    handler = UploadPackHandler(backend, [path], proto)
    # FIXME: Catch exceptions and write a single-line summary to outf.
    handler.handle()
    return 0


def receive_pack(path=".", inf=None, outf=None):
    """Receive a pack file after negotiating its contents using smart protocol.

    :param path: Path to the repository
    :param inf: Input stream to communicate with client
    :param outf: Output stream to communicate with client
    """
    if outf is None:
        outf = getattr(sys.stdout, 'buffer', sys.stdout)
    if inf is None:
        inf = getattr(sys.stdin, 'buffer', sys.stdin)
    path = os.path.expanduser(path)
    backend = FileSystemBackend(path)

    def send_fn(data):
        outf.write(data)
        outf.flush()
    proto = Protocol(inf.read, send_fn)
    handler = ReceivePackHandler(backend, [path], proto)
    # FIXME: Catch exceptions and write a single-line summary to outf.
    handler.handle()
    return 0


def _make_branch_ref(name):
    if getattr(name, 'encode', None):
        name = name.encode(DEFAULT_ENCODING)
    return b"refs/heads/" + name


def _make_tag_ref(name):
    if getattr(name, 'encode', None):
        name = name.encode(DEFAULT_ENCODING)
    return b"refs/tags/" + name


def branch_delete(repo, name):
    """Delete a branch.

    :param repo: Path to the repository
    :param name: Name of the branch
    """
    with open_repo_closing(repo) as r:
        if isinstance(name, list):
            names = name
        else:
            names = [name]
        for name in names:
            del r.refs[_make_branch_ref(name)]


def branch_create(repo, name, objectish=None, force=False):
    """Create a branch.

    :param repo: Path to the repository
    :param name: Name of the new branch
    :param objectish: Target object to point new branch at (defaults to HEAD)
    :param force: Force creation of branch, even if it already exists
    """
    with open_repo_closing(repo) as r:
        if objectish is None:
            objectish = "HEAD"
        object = parse_object(r, objectish)
        refname = _make_branch_ref(name)
        ref_message = b"branch: Created from " + objectish.encode('utf-8')
        if force:
            r.refs.set_if_equals(refname, None, object.id, message=ref_message)
        else:
            if not r.refs.add_if_new(refname, object.id, message=ref_message):
                raise KeyError("Branch with name %s already exists." % name)


def branch_list(repo):
    """List all branches.

    :param repo: Path to the repository
    """
    with open_repo_closing(repo) as r:
        return r.refs.keys(base=b"refs/heads/")


def fetch(repo, remote_location, remote_name=b'origin', outstream=sys.stdout,
          errstream=default_bytes_err_stream, message=None, depth=None,
          prune=False, prune_tags=False, **kwargs):
    """Fetch objects from a remote server.

    :param repo: Path to the repository
    :param remote_location: String identifying a remote server
    :param remote_name: Name for remote server
    :param outstream: Output stream (defaults to stdout)
    :param errstream: Error stream (defaults to stderr)
    :param message: Reflog message (defaults to b"fetch: from <remote_name>")
    :param depth: Depth to fetch at
    :param prune: Prune remote removed refs
    :param prune_tags: Prune reomte removed tags
    :return: Dictionary with refs on the remote
    """
    if message is None:
        message = b'fetch: from ' + remote_location.encode("utf-8")
    with open_repo_closing(repo) as r:
        client, path = get_transport_and_path(
            remote_location, config=r.get_config_stack(), **kwargs)
        fetch_result = client.fetch(path, r, progress=errstream.write,
                                    depth=depth)
        stripped_refs = strip_peeled_refs(fetch_result.refs)
        branches = {
            n[len(b'refs/heads/'):]: v for (n, v) in stripped_refs.items()
            if n.startswith(b'refs/heads/')}
        r.refs.import_refs(
            b'refs/remotes/' + remote_name, branches, message=message,
            prune=prune)
        tags = {
            n[len(b'refs/tags/'):]: v for (n, v) in stripped_refs.items()
            if n.startswith(b'refs/tags/') and
            not n.endswith(ANNOTATED_TAG_SUFFIX)}
        r.refs.import_refs(
            b'refs/tags', tags, message=message,
            prune=prune_tags)
    return fetch_result.refs


def ls_remote(remote, config=None, **kwargs):
    """List the refs in a remote.

    :param remote: Remote repository location
    :param config: Configuration to use
    :return: Dictionary with remote refs
    """
    if config is None:
        config = StackedConfig.default()
    client, host_path = get_transport_and_path(remote, config=config, **kwargs)
    return client.get_refs(host_path)


def repack(repo):
    """Repack loose files in a repository.

    Currently this only packs loose objects.

    :param repo: Path to the repository
    """
    with open_repo_closing(repo) as r:
        r.object_store.pack_loose_objects()


def pack_objects(repo, object_ids, packf, idxf, delta_window_size=None):
    """Pack objects into a file.

    :param repo: Path to the repository
    :param object_ids: List of object ids to write
    :param packf: File-like object to write to
    :param idxf: File-like object to write to (can be None)
    """
    with open_repo_closing(repo) as r:
        entries, data_sum = write_pack_objects(
            packf,
            r.object_store.iter_shas((oid, None) for oid in object_ids),
            delta_window_size=delta_window_size)
    if idxf is not None:
        entries = sorted([(k, v[0], v[1]) for (k, v) in entries.items()])
        write_pack_index(idxf, entries, data_sum)


def ls_tree(repo, treeish=b"HEAD", outstream=sys.stdout, recursive=False,
            name_only=False):
    """List contents of a tree.

    :param repo: Path to the repository
    :param tree_ish: Tree id to list
    :param outstream: Output stream (defaults to stdout)
    :param recursive: Whether to recursively list files
    :param name_only: Only print item name
    """
    def list_tree(store, treeid, base):
        for (name, mode, sha) in store[treeid].iteritems():
            if base:
                name = posixpath.join(base, name)
            if name_only:
                outstream.write(name + b"\n")
            else:
                outstream.write(pretty_format_tree_entry(name, mode, sha))
            if stat.S_ISDIR(mode) and recursive:
                list_tree(store, sha, name)
    with open_repo_closing(repo) as r:
        tree = parse_tree(r, treeish)
        list_tree(r.object_store, tree.id, "")


def remote_add(repo, name, url):
    """Add a remote.

    :param repo: Path to the repository
    :param name: Remote name
    :param url: Remote URL
    """
    if not isinstance(name, bytes):
        name = name.encode(DEFAULT_ENCODING)
    if not isinstance(url, bytes):
        url = url.encode(DEFAULT_ENCODING)
    with open_repo_closing(repo) as r:
        c = r.get_config()
        section = (b'remote', name)
        if c.has_section(section):
            raise RemoteExists(section)
        c.set(section, b"url", url)
        c.write_to_path()


def check_ignore(repo, paths, no_index=False):
    """Debug gitignore files.

    :param repo: Path to the repository
    :param paths: List of paths to check for
    :param no_index: Don't check index
    :return: List of ignored files
    """
    with open_repo_closing(repo) as r:
        index = r.open_index()
        ignore_manager = IgnoreFilterManager.from_repo(r)
        for path in paths:
            if not no_index and path_to_tree_path(r.path, path) in index:
                continue
            if os.path.isabs(path):
                path = os.path.relpath(path, r.path)
            if ignore_manager.is_ignored(path):
                yield path


def update_head(repo, target, detached=False, new_branch=None):
    """Update HEAD to point at a new branch/commit.

    Note that this does not actually update the working tree.

    :param repo: Path to the repository
    :param detach: Create a detached head
    :param target: Branch or committish to switch to
    :param new_branch: New branch to create
    """
    with open_repo_closing(repo) as r:
        if new_branch is not None:
            to_set = _make_branch_ref(new_branch)
        else:
            to_set = b"HEAD"
        if detached:
            # TODO(user): Provide some way so that the actual ref gets
            # updated rather than what it points to, so the delete isn't
            # necessary.
            del r.refs[to_set]
            r.refs[to_set] = parse_commit(r, target).id
        else:
            r.refs.set_symbolic_ref(to_set, parse_ref(r, target))
        if new_branch is not None:
            r.refs.set_symbolic_ref(b"HEAD", to_set)


def check_mailmap(repo, contact):
    """Check canonical name and email of contact.

    :param repo: Path to the repository
    :param contact: Contact name and/or email
    :return: Canonical contact data
    """
    with open_repo_closing(repo) as r:
        from dulwich.mailmap import Mailmap
        import errno
        try:
            mailmap = Mailmap.from_path(os.path.join(r.path, '.mailmap'))
        except IOError as e:
            if e.errno != errno.ENOENT:
                raise
            mailmap = Mailmap()
        return mailmap.lookup(contact)


def fsck(repo):
    """Check a repository.

    :param repo: A path to the repository
    :return: Iterator over errors/warnings
    """
    with open_repo_closing(repo) as r:
        # TODO(user): check pack files
        # TODO(user): check graph
        # TODO(user): check refs
        for sha in r.object_store:
            o = r.object_store[sha]
            try:
                o.check()
            except Exception as e:
                yield (sha, e)


def stash_list(repo):
    """List all stashes in a repository."""
    with open_repo_closing(repo) as r:
        from dulwich.stash import Stash
        stash = Stash.from_repo(r)
        return enumerate(list(stash.stashes()))


def stash_push(repo):
    """Push a new stash onto the stack."""
    with open_repo_closing(repo) as r:
        from dulwich.stash import Stash
        stash = Stash.from_repo(r)
        stash.push()


def stash_pop(repo):
    """Pop a new stash from the stack."""
    with open_repo_closing(repo) as r:
        from dulwich.stash import Stash
        stash = Stash.from_repo(r)
        stash.pop()


def ls_files(repo):
    """List all files in an index."""
    with open_repo_closing(repo) as r:
        return sorted(r.open_index())


def describe(repo):
    """Describe the repository version.

    :param projdir: git repository root
    :returns: a string description of the current git revision

    Examples: "gabcdefh", "v0.1" or "v0.1-5-gabcdefh".
    """
    # Get the repository
    with open_repo_closing(repo) as r:
        # Get a list of all tags
        refs = r.get_refs()
        tags = {}
        for key, value in refs.items():
            key = key.decode()
            obj = r.get_object(value)
            if u'tags' not in key:
                continue

            _, tag = key.rsplit(u'/', 1)

            try:
                commit = obj.object
            except AttributeError:
                continue
            else:
                commit = r.get_object(commit[1])
            tags[tag] = [
                datetime.datetime(*time.gmtime(commit.commit_time)[:6]),
                commit.id.decode('ascii'),
            ]

        sorted_tags = sorted(tags.items(),
                             key=lambda tag: tag[1][0],
                             reverse=True)

        # If there are no tags, return the current commit
        if len(sorted_tags) == 0:
            return 'g{}'.format(r[r.head()].id.decode('ascii')[:7])

        # We're now 0 commits from the top
        commit_count = 0

        # Get the latest commit
        latest_commit = r[r.head()]

        # Walk through all commits
        walker = r.get_walker()
        for entry in walker:
            # Check if tag
            commit_id = entry.commit.id.decode('ascii')
            for tag in sorted_tags:
                tag_name = tag[0]
                tag_commit = tag[1][1]
                if commit_id == tag_commit:
                    if commit_count == 0:
                        return tag_name
                    else:
                        return '{}-{}-g{}'.format(
                                tag_name,
                                commit_count,
                                latest_commit.id.decode('ascii')[:7])

            commit_count += 1

        # Return plain commit if no parent tag can be found
        return 'g{}'.format(latest_commit.id.decode('ascii')[:7])


def get_object_by_path(repo, path, committish=None):
    """Get an object by path.

    :param repo: A path to the repository
    :param path: Path to look up
    :param committish: Commit to look up path in
    :return: A `ShaFile` object
    """
    if committish is None:
        committish = "HEAD"
    # Get the repository
    with open_repo_closing(repo) as r:
        commit = parse_commit(r, committish)
        base_tree = commit.tree
        if not isinstance(path, bytes):
            path = path.encode(commit.encoding or DEFAULT_ENCODING)
        (mode, sha) = tree_lookup_path(
            r.object_store.__getitem__,
            base_tree, path)
        return r[sha]


def write_tree(repo):
    """Write a tree object from the index.

    :param repo: Repository for which to write tree
    :return: tree id for the tree that was written
    """
    with open_repo_closing(repo) as r:
        return r.open_index().commit(r.object_store)
