vcsserver/git.py

# RhodeCode VCSServer provides access to different vcs backends via network.
# Copyright (C) 2014-2019 RhodeCode GmbH
#
# 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 3 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 Street, Fifth Floor, Boston, MA 02110-1301  USA
import collections
import logging
import os
import posixpath as vcspath
import re
import stat
import traceback
import urllib
import urllib2
from functools import wraps

import more_itertools
import pygit2
from pygit2 import Repository as LibGit2Repo
from dulwich import index, objects
from dulwich.client import HttpGitClient, LocalGitClient
from dulwich.errors import (
    NotGitRepository, ChecksumMismatch, WrongObjectException,
    MissingCommitError, ObjectMissing, HangupException,
    UnexpectedCommandError)
from dulwich.repo import Repo as DulwichRepo
from dulwich.server import update_server_info

from vcsserver import exceptions, settings, subprocessio
from vcsserver.utils import safe_str
from vcsserver.base import RepoFactory, obfuscate_qs, raise_from_original
from vcsserver.hgcompat import (
    hg_url as url_parser, httpbasicauthhandler, httpdigestauthhandler)
from vcsserver.git_lfs.lib import LFSOidStore

DIR_STAT = stat.S_IFDIR
FILE_MODE = stat.S_IFMT
GIT_LINK = objects.S_IFGITLINK

log = logging.getLogger(__name__)


def reraise_safe_exceptions(func):
    """Converts Dulwich exceptions to something neutral."""

    @wraps(func)
    def wrapper(*args, **kwargs):
        try:
            return func(*args, **kwargs)
        except (ChecksumMismatch, WrongObjectException, MissingCommitError, ObjectMissing,) as e:
            exc = exceptions.LookupException(org_exc=e)
            raise exc(safe_str(e))
        except (HangupException, UnexpectedCommandError) as e:
            exc = exceptions.VcsException(org_exc=e)
            raise exc(safe_str(e))
        except Exception as e:
            # NOTE(marcink): becuase of how dulwich handles some exceptions
            # (KeyError on empty repos), we cannot track this and catch all
            # exceptions, it's an exceptions from other handlers
            #if not hasattr(e, '_vcs_kind'):
                #log.exception("Unhandled exception in git remote call")
                #raise_from_original(exceptions.UnhandledException)
            raise
    return wrapper


class Repo(DulwichRepo):
    """
    A wrapper for dulwich Repo class.

    Since dulwich is sometimes keeping .idx file descriptors open, it leads to
    "Too many open files" error. We need to close all opened file descriptors
    once the repo object is destroyed.
    """
    def __del__(self):
        if hasattr(self, 'object_store'):
            self.close()


class Repository(LibGit2Repo):

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.free()


class GitFactory(RepoFactory):
    repo_type = 'git'

    def _create_repo(self, wire, create, use_libgit2=False):
        if use_libgit2:
            return Repository(wire['path'])
        else:
            repo_path = str_to_dulwich(wire['path'])
            return Repo(repo_path)

    def repo(self, wire, create=False, use_libgit2=False):
        """
        Get a repository instance for the given path.
        """
        region = self._cache_region
        context = wire.get('context', None)
        repo_path = wire.get('path', '')
        context_uid = '{}'.format(context)
        cache = wire.get('cache', True)
        cache_on = context and cache

        @region.conditional_cache_on_arguments(condition=cache_on)
        def create_new_repo(_repo_type, _repo_path, _context_uid, _use_libgit2):
            return self._create_repo(wire, create, use_libgit2)

        repo = create_new_repo(self.repo_type, repo_path, context_uid, use_libgit2)
        return repo

    def repo_libgit2(self, wire):
        return self.repo(wire, use_libgit2=True)


class GitRemote(object):

    def __init__(self, factory):
        self._factory = factory
        self.peeled_ref_marker = '^{}'
        self._bulk_methods = {
            "date": self.date,
            "author": self.author,
            "message": self.message,
            "parents": self.parents,
            "_commit": self.revision,
        }

    def _wire_to_config(self, wire):
        if 'config' in wire:
            return dict([(x[0] + '_' + x[1], x[2]) for x in wire['config']])
        return {}

    def _remote_conf(self, config):
        params = [
            '-c', 'core.askpass=""',
        ]
        ssl_cert_dir = config.get('vcs_ssl_dir')
        if ssl_cert_dir:
            params.extend(['-c', 'http.sslCAinfo={}'.format(ssl_cert_dir)])
        return params

    @reraise_safe_exceptions
    def is_empty(self, wire):
        repo = self._factory.repo_libgit2(wire)

        try:
            has_head = repo.head.name
            if has_head:
                return False

            # NOTE(marcink): check again using more expensive method
            return repo.is_empty
        except Exception:
            pass

        return True

    @reraise_safe_exceptions
    def add_object(self, wire, content):
        repo = self._factory.repo(wire)
        blob = objects.Blob()
        blob.set_raw_string(content)
        repo.object_store.add_object(blob)
        return blob.id

    @reraise_safe_exceptions
    def assert_correct_path(self, wire):
        try:
            self._factory.repo_libgit2(wire)
        except pygit2.GitError:
            path = wire.get('path')
            tb = traceback.format_exc()
            log.debug("Invalid Git path `%s`, tb: %s", path, tb)
            return False

        return True

    @reraise_safe_exceptions
    def bare(self, wire):
        repo = self._factory.repo_libgit2(wire)
        return repo.is_bare

    @reraise_safe_exceptions
    def blob_as_pretty_string(self, wire, sha):
        repo_init = self._factory.repo_libgit2(wire)
        with repo_init as repo:
            blob_obj = repo[sha]
            blob = blob_obj.data
            return blob

    @reraise_safe_exceptions
    def blob_raw_length(self, wire, sha):
        repo_init = self._factory.repo_libgit2(wire)
        with repo_init as repo:
            blob = repo[sha]
            return blob.size

    def _parse_lfs_pointer(self, raw_content):

        spec_string = 'version https://git-lfs.github.com/spec'
        if raw_content and raw_content.startswith(spec_string):
            pattern = re.compile(r"""
            (?:\n)?
            ^version[ ]https://git-lfs\.github\.com/spec/(?P<spec_ver>v\d+)\n
            ^oid[ ] sha256:(?P<oid_hash>[0-9a-f]{64})\n
            ^size[ ](?P<oid_size>[0-9]+)\n
            (?:\n)?
            """, re.VERBOSE | re.MULTILINE)
            match = pattern.match(raw_content)
            if match:
                return match.groupdict()

        return {}

    @reraise_safe_exceptions
    def is_large_file(self, wire, sha):
        repo_init = self._factory.repo_libgit2(wire)

        with repo_init as repo:
            blob = repo[sha]
            if blob.is_binary:
                return {}

            return self._parse_lfs_pointer(blob.data)

    @reraise_safe_exceptions
    def in_largefiles_store(self, wire, oid):
        repo = self._factory.repo_libgit2(wire)
        conf = self._wire_to_config(wire)

        store_location = conf.get('vcs_git_lfs_store_location')
        if store_location:
            repo_name = repo.path
            store = LFSOidStore(
                oid=oid, repo=repo_name, store_location=store_location)
            return store.has_oid()

        return False

    @reraise_safe_exceptions
    def store_path(self, wire, oid):
        repo = self._factory.repo_libgit2(wire)
        conf = self._wire_to_config(wire)

        store_location = conf.get('vcs_git_lfs_store_location')
        if store_location:
            repo_name = repo.path
            store = LFSOidStore(
                oid=oid, repo=repo_name, store_location=store_location)
            return store.oid_path
        raise ValueError('Unable to fetch oid with path {}'.format(oid))

    @reraise_safe_exceptions
    def bulk_request(self, wire, rev, pre_load):
        result = {}
        for attr in pre_load:
            try:
                method = self._bulk_methods[attr]
                args = [wire, rev]
                result[attr] = method(*args)
            except KeyError as e:
                raise exceptions.VcsException(e)("Unknown bulk attribute: %s" % attr)
        return result

    def _build_opener(self, url):
        handlers = []
        url_obj = url_parser(url)
        _, authinfo = url_obj.authinfo()

        if authinfo:
            # create a password manager
            passmgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
            passmgr.add_password(*authinfo)

            handlers.extend((httpbasicauthhandler(passmgr),
                             httpdigestauthhandler(passmgr)))

        return urllib2.build_opener(*handlers)

    def _type_id_to_name(self, type_id):
        return {
            1: b'commit',
            2: b'tree',
            3: b'blob',
            4: b'tag'
        }[type_id]

    @reraise_safe_exceptions
    def check_url(self, url, config):
        url_obj = url_parser(url)
        test_uri, _ = url_obj.authinfo()
        url_obj.passwd = '*****' if url_obj.passwd else url_obj.passwd
        url_obj.query = obfuscate_qs(url_obj.query)
        cleaned_uri = str(url_obj)
        log.info("Checking URL for remote cloning/import: %s", cleaned_uri)

        if not test_uri.endswith('info/refs'):
            test_uri = test_uri.rstrip('/') + '/info/refs'

        o = self._build_opener(url)
        o.addheaders = [('User-Agent', 'git/1.7.8.0')]  # fake some git

        q = {"service": 'git-upload-pack'}
        qs = '?%s' % urllib.urlencode(q)
        cu = "%s%s" % (test_uri, qs)
        req = urllib2.Request(cu, None, {})

        try:
            log.debug("Trying to open URL %s", cleaned_uri)
            resp = o.open(req)
            if resp.code != 200:
                raise exceptions.URLError()('Return Code is not 200')
        except Exception as e:
            log.warning("URL cannot be opened: %s", cleaned_uri, exc_info=True)
            # means it cannot be cloned
            raise exceptions.URLError(e)("[%s] org_exc: %s" % (cleaned_uri, e))

        # now detect if it's proper git repo
        gitdata = resp.read()
        if 'service=git-upload-pack' in gitdata:
            pass
        elif re.findall(r'[0-9a-fA-F]{40}\s+refs', gitdata):
            # old style git can return some other format !
            pass
        else:
            raise exceptions.URLError()(
                "url [%s] does not look like an git" % (cleaned_uri,))

        return True

    @reraise_safe_exceptions
    def clone(self, wire, url, deferred, valid_refs, update_after_clone):
        # TODO(marcink): deprecate this method. Last i checked we don't use it anymore
        remote_refs = self.pull(wire, url, apply_refs=False)
        repo = self._factory.repo(wire)
        if isinstance(valid_refs, list):
            valid_refs = tuple(valid_refs)

        for k in remote_refs:
            # only parse heads/tags and skip so called deferred tags
            if k.startswith(valid_refs) and not k.endswith(deferred):
                repo[k] = remote_refs[k]

        if update_after_clone:
            # we want to checkout HEAD
            repo["HEAD"] = remote_refs["HEAD"]
            index.build_index_from_tree(repo.path, repo.index_path(),
                                        repo.object_store, repo["HEAD"].tree)

    # TODO: this is quite complex, check if that can be simplified
    @reraise_safe_exceptions
    def commit(self, wire, commit_data, branch, commit_tree, updated, removed):
        repo = self._factory.repo(wire)
        object_store = repo.object_store

        # Create tree and populates it with blobs
        commit_tree = commit_tree and repo[commit_tree] or objects.Tree()

        for node in updated:
            # Compute subdirs if needed
            dirpath, nodename = vcspath.split(node['path'])
            dirnames = map(safe_str, dirpath and dirpath.split('/') or [])
            parent = commit_tree
            ancestors = [('', parent)]

            # Tries to dig for the deepest existing tree
            while dirnames:
                curdir = dirnames.pop(0)
                try:
                    dir_id = parent[curdir][1]
                except KeyError:
                    # put curdir back into dirnames and stops
                    dirnames.insert(0, curdir)
                    break
                else:
                    # If found, updates parent
                    parent = repo[dir_id]
                    ancestors.append((curdir, parent))
            # Now parent is deepest existing tree and we need to create
            # subtrees for dirnames (in reverse order)
            # [this only applies for nodes from added]
            new_trees = []

            blob = objects.Blob.from_string(node['content'])

            if dirnames:
                # If there are trees which should be created we need to build
                # them now (in reverse order)
                reversed_dirnames = list(reversed(dirnames))
                curtree = objects.Tree()
                curtree[node['node_path']] = node['mode'], blob.id
                new_trees.append(curtree)
                for dirname in reversed_dirnames[:-1]:
                    newtree = objects.Tree()
                    newtree[dirname] = (DIR_STAT, curtree.id)
                    new_trees.append(newtree)
                    curtree = newtree
                parent[reversed_dirnames[-1]] = (DIR_STAT, curtree.id)
            else:
                parent.add(name=node['node_path'], mode=node['mode'], hexsha=blob.id)

            new_trees.append(parent)
            # Update ancestors
            reversed_ancestors = reversed(
                [(a[1], b[1], b[0]) for a, b in zip(ancestors, ancestors[1:])])
            for parent, tree, path in reversed_ancestors:
                parent[path] = (DIR_STAT, tree.id)
                object_store.add_object(tree)

            object_store.add_object(blob)
            for tree in new_trees:
                object_store.add_object(tree)

        for node_path in removed:
            paths = node_path.split('/')
            tree = commit_tree
            trees = [tree]
            # Traverse deep into the forest...
            for path in paths:
                try:
                    obj = repo[tree[path][1]]
                    if isinstance(obj, objects.Tree):
                        trees.append(obj)
                        tree = obj
                except KeyError:
                    break
            # Cut down the blob and all rotten trees on the way back...
            for path, tree in reversed(zip(paths, trees)):
                del tree[path]
                if tree:
                    # This tree still has elements - don't remove it or any
                    # of it's parents
                    break

        object_store.add_object(commit_tree)

        # Create commit
        commit = objects.Commit()
        commit.tree = commit_tree.id
        for k, v in commit_data.iteritems():
            setattr(commit, k, v)
        object_store.add_object(commit)

        self.create_branch(wire, branch, commit.id)

        # dulwich set-ref
        ref = 'refs/heads/%s' % branch
        repo.refs[ref] = commit.id

        return commit.id

    @reraise_safe_exceptions
    def pull(self, wire, url, apply_refs=True, refs=None, update_after=False):
        if url != 'default' and '://' not in url:
            client = LocalGitClient(url)
        else:
            url_obj = url_parser(url)
            o = self._build_opener(url)
            url, _ = url_obj.authinfo()
            client = HttpGitClient(base_url=url, opener=o)
        repo = self._factory.repo(wire)

        determine_wants = repo.object_store.determine_wants_all
        if refs:
            def determine_wants_requested(references):
                return [references[r] for r in references if r in refs]
            determine_wants = determine_wants_requested

        try:
            remote_refs = client.fetch(
                path=url, target=repo, determine_wants=determine_wants)
        except NotGitRepository as e:
            log.warning(
                'Trying to fetch from "%s" failed, not a Git repository.', url)
            # Exception can contain unicode which we convert
            raise exceptions.AbortException(e)(repr(e))

        # mikhail: client.fetch() returns all the remote refs, but fetches only
        # refs filtered by `determine_wants` function. We need to filter result
        # as well
        if refs:
            remote_refs = {k: remote_refs[k] for k in remote_refs if k in refs}

        if apply_refs:
            # TODO: johbo: Needs proper test coverage with a git repository
            # that contains a tag object, so that we would end up with
            # a peeled ref at this point.
            for k in remote_refs:
                if k.endswith(self.peeled_ref_marker):
                    log.debug("Skipping peeled reference %s", k)
                    continue
                repo[k] = remote_refs[k]

            if refs and not update_after:
                # mikhail: explicitly set the head to the last ref.
                repo['HEAD'] = remote_refs[refs[-1]]

        if update_after:
            # we want to checkout HEAD
            repo["HEAD"] = remote_refs["HEAD"]
            index.build_index_from_tree(repo.path, repo.index_path(),
                                        repo.object_store, repo["HEAD"].tree)
        return remote_refs

    @reraise_safe_exceptions
    def sync_fetch(self, wire, url, refs=None):
        repo = self._factory.repo(wire)
        if refs and not isinstance(refs, (list, tuple)):
            refs = [refs]
        config = self._wire_to_config(wire)
        # get all remote refs we'll use to fetch later
        output, __ = self.run_git_command(
            wire, ['ls-remote', url], fail_on_stderr=False,
            _copts=self._remote_conf(config),
            extra_env={'GIT_TERMINAL_PROMPT': '0'})

        remote_refs = collections.OrderedDict()
        fetch_refs = []

        for ref_line in output.splitlines():
            sha, ref = ref_line.split('\t')
            sha = sha.strip()
            if ref in remote_refs:
                # duplicate, skip
                continue
            if ref.endswith(self.peeled_ref_marker):
                log.debug("Skipping peeled reference %s", ref)
                continue
            # don't sync HEAD
            if ref in ['HEAD']:
                continue

            remote_refs[ref] = sha

            if refs and sha in refs:
                # we filter fetch using our specified refs
                fetch_refs.append('{}:{}'.format(ref, ref))
            elif not refs:
                fetch_refs.append('{}:{}'.format(ref, ref))
        log.debug('Finished obtaining fetch refs, total: %s', len(fetch_refs))
        if fetch_refs:
            for chunk in more_itertools.chunked(fetch_refs, 1024 * 4):
                fetch_refs_chunks = list(chunk)
                log.debug('Fetching %s refs from import url', len(fetch_refs_chunks))
                _out, _err = self.run_git_command(
                    wire, ['fetch', url, '--force', '--prune', '--'] + fetch_refs_chunks,
                    fail_on_stderr=False,
                    _copts=self._remote_conf(config),
                    extra_env={'GIT_TERMINAL_PROMPT': '0'})

        return remote_refs

    @reraise_safe_exceptions
    def sync_push(self, wire, url, refs=None):
        if not self.check_url(url, wire):
            return
        config = self._wire_to_config(wire)
        repo = self._factory.repo(wire)
        self.run_git_command(
            wire, ['push', url, '--mirror'], fail_on_stderr=False,
            _copts=self._remote_conf(config),
            extra_env={'GIT_TERMINAL_PROMPT': '0'})

    @reraise_safe_exceptions
    def get_remote_refs(self, wire, url):
        repo = Repo(url)
        return repo.get_refs()

    @reraise_safe_exceptions
    def get_description(self, wire):
        repo = self._factory.repo(wire)
        return repo.get_description()

    @reraise_safe_exceptions
    def get_missing_revs(self, wire, rev1, rev2, path2):
        repo = self._factory.repo(wire)
        LocalGitClient(thin_packs=False).fetch(path2, repo)

        wire_remote = wire.copy()
        wire_remote['path'] = path2
        repo_remote = self._factory.repo(wire_remote)
        LocalGitClient(thin_packs=False).fetch(wire["path"], repo_remote)

        revs = [
            x.commit.id
            for x in repo_remote.get_walker(include=[rev2], exclude=[rev1])]
        return revs

    @reraise_safe_exceptions
    def get_object(self, wire, sha):
        repo = self._factory.repo_libgit2(wire)

        missing_commit_err = 'Commit {} does not exist for `{}`'.format(sha, wire['path'])
        try:
            commit = repo.revparse_single(sha)
        except (KeyError, ValueError) as e:
            raise exceptions.LookupException(e)(missing_commit_err)

        if isinstance(commit, pygit2.Tag):
            commit = repo.get(commit.target)

        # check for dangling commit
        branches = [x for x in repo.branches.with_commit(commit.hex)]
        if not branches:
            raise exceptions.LookupException(None)(missing_commit_err)

        commit_id = commit.hex
        type_id = commit.type

        return {
            'id': commit_id,
            'type': self._type_id_to_name(type_id),
            'commit_id': commit_id,
            'idx': 0
        }

    @reraise_safe_exceptions
    def get_refs(self, wire):
        repo = self._factory.repo_libgit2(wire)

        result = {}
        for ref in repo.references:
            peeled_sha = repo.lookup_reference(ref).peel()
            result[ref] = peeled_sha.hex

        return result

    @reraise_safe_exceptions
    def head(self, wire, show_exc=True):
        repo = self._factory.repo_libgit2(wire)
        try:
            return repo.head.peel().hex
        except Exception:
            if show_exc:
                raise

    @reraise_safe_exceptions
    def init(self, wire):
        repo_path = str_to_dulwich(wire['path'])
        self.repo = Repo.init(repo_path)

    @reraise_safe_exceptions
    def init_bare(self, wire):
        repo_path = str_to_dulwich(wire['path'])
        self.repo = Repo.init_bare(repo_path)

    @reraise_safe_exceptions
    def revision(self, wire, rev):
        repo = self._factory.repo_libgit2(wire)
        commit = repo[rev]
        obj_data = {
            'id': commit.id.hex,
        }
        # tree objects itself don't have tree_id attribute
        if hasattr(commit, 'tree_id'):
            obj_data['tree'] = commit.tree_id.hex

        return obj_data

    @reraise_safe_exceptions
    def date(self, wire, rev):
        repo = self._factory.repo_libgit2(wire)
        commit = repo[rev]
        # TODO(marcink): check dulwich difference of offset vs timezone
        return [commit.commit_time, commit.commit_time_offset]

    @reraise_safe_exceptions
    def author(self, wire, rev):
        repo = self._factory.repo_libgit2(wire)
        commit = repo[rev]
        if commit.author.email:
            return u"{} <{}>".format(commit.author.name, commit.author.email)

        return u"{}".format(commit.author.raw_name)

    @reraise_safe_exceptions
    def message(self, wire, rev):
        repo = self._factory.repo_libgit2(wire)
        commit = repo[rev]
        return commit.message

    @reraise_safe_exceptions
    def parents(self, wire, rev):
        repo = self._factory.repo_libgit2(wire)
        commit = repo[rev]
        return [x.hex for x in commit.parent_ids]

    @reraise_safe_exceptions
    def set_refs(self, wire, key, value):
        repo = self._factory.repo_libgit2(wire)
        repo.references.create(key, value, force=True)

    @reraise_safe_exceptions
    def create_branch(self, wire, branch_name, commit_id, force=False):
        repo = self._factory.repo_libgit2(wire)
        commit = repo[commit_id]

        if force:
            repo.branches.local.create(branch_name, commit, force=force)
        elif not repo.branches.get(branch_name):
            # create only if that branch isn't existing
            repo.branches.local.create(branch_name, commit, force=force)

    @reraise_safe_exceptions
    def remove_ref(self, wire, key):
        repo = self._factory.repo_libgit2(wire)
        repo.references.delete(key)

    @reraise_safe_exceptions
    def tag_remove(self, wire, tag_name):
        repo = self._factory.repo_libgit2(wire)
        key = 'refs/tags/{}'.format(tag_name)
        repo.references.delete(key)

    @reraise_safe_exceptions
    def tree_changes(self, wire, source_id, target_id):
        # TODO(marcink): remove this seems it's only used by tests
        repo = self._factory.repo(wire)
        source = repo[source_id].tree if source_id else None
        target = repo[target_id].tree
        result = repo.object_store.tree_changes(source, target)
        return list(result)

    @reraise_safe_exceptions
    def tree_and_type_for_path(self, wire, commit_id, path):
        repo_init = self._factory.repo_libgit2(wire)

        with repo_init as repo:
            commit = repo[commit_id]
            try:
                tree = commit.tree[path]
            except KeyError:
                return None, None, None

            return tree.id.hex, tree.type, tree.filemode

    @reraise_safe_exceptions
    def tree_items(self, wire, tree_id):
        repo_init = self._factory.repo_libgit2(wire)

        with repo_init as repo:
            try:
                tree = repo[tree_id]
            except KeyError:
                raise ObjectMissing('No tree with id: {}'.format(tree_id))

            result = []
            for item in tree:
                item_sha = item.hex
                item_mode = item.filemode
                item_type = item.type

                if item_type == 'commit':
                    # NOTE(marcink): submodules we translate to 'link' for backward compat
                    item_type = 'link'

                result.append((item.name, item_mode, item_sha, item_type))
            return result

    @reraise_safe_exceptions
    def update_server_info(self, wire):
        repo = self._factory.repo(wire)
        update_server_info(repo)

    @reraise_safe_exceptions
    def discover_git_version(self):
        stdout, _ = self.run_git_command(
            {}, ['--version'], _bare=True, _safe=True)
        prefix = 'git version'
        if stdout.startswith(prefix):
            stdout = stdout[len(prefix):]
        return stdout.strip()

    @reraise_safe_exceptions
    def get_all_commit_ids(self, wire):

        cmd = ['rev-list', '--reverse', '--date-order', '--branches', '--tags']
        try:
            output, __ = self.run_git_command(wire, cmd)
            return output.splitlines()
        except Exception:
            # Can be raised for empty repositories
            return []

    @reraise_safe_exceptions
    def run_git_command(self, wire, cmd, **opts):
        path = wire.get('path', None)

        if path and os.path.isdir(path):
            opts['cwd'] = path

        if '_bare' in opts:
            _copts = []
            del opts['_bare']
        else:
            _copts = ['-c', 'core.quotepath=false', ]
        safe_call = False
        if '_safe' in opts:
            # no exc on failure
            del opts['_safe']
            safe_call = True

        if '_copts' in opts:
            _copts.extend(opts['_copts'] or [])
            del opts['_copts']

        gitenv = os.environ.copy()
        gitenv.update(opts.pop('extra_env', {}))
        # need to clean fix GIT_DIR !
        if 'GIT_DIR' in gitenv:
            del gitenv['GIT_DIR']
        gitenv['GIT_CONFIG_NOGLOBAL'] = '1'
        gitenv['GIT_DISCOVERY_ACROSS_FILESYSTEM'] = '1'

        cmd = [settings.GIT_EXECUTABLE] + _copts + cmd
        _opts = {'env': gitenv, 'shell': False}

        try:
            _opts.update(opts)
            p = subprocessio.SubprocessIOChunker(cmd, **_opts)

            return ''.join(p), ''.join(p.error)
        except (EnvironmentError, OSError) as err:
            cmd = ' '.join(cmd)  # human friendly CMD
            tb_err = ("Couldn't run git command (%s).\n"
                      "Original error was:%s\n"
                      "Call options:%s\n"
                      % (cmd, err, _opts))
            log.exception(tb_err)
            if safe_call:
                return '', err
            else:
                raise exceptions.VcsException()(tb_err)

    @reraise_safe_exceptions
    def install_hooks(self, wire, force=False):
        from vcsserver.hook_utils import install_git_hooks
        repo = self._factory.repo(wire)
        return install_git_hooks(repo.path, repo.bare, force_create=force)

    @reraise_safe_exceptions
    def get_hooks_info(self, wire):
        from vcsserver.hook_utils import (
            get_git_pre_hook_version, get_git_post_hook_version)
        repo = self._factory.repo(wire)
        return {
            'pre_version': get_git_pre_hook_version(repo.path, repo.bare),
            'post_version': get_git_post_hook_version(repo.path, repo.bare),
        }


def str_to_dulwich(value):
    """
    Dulwich 0.10.1a requires `unicode` objects to be passed in.
    """
    return value.decode(settings.WIRE_ENCODING)