/usr/share/pyshared/dulwich/refs.py is in python-dulwich 0.9.4-1.
This file is owned by root:root, with mode 0o644.
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# Copyright (C) 2008-2013 Jelmer Vernooij <jelmer@samba.org>
#
# 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; version 2
# of the License or (at your option) any later version of
# the License.
#
# 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.
"""Ref handling.
"""
import errno
import os
from dulwich.errors import (
PackedRefsException,
RefFormatError,
)
from dulwich.objects import (
hex_to_sha,
)
from dulwich.file import (
GitFile,
ensure_dir_exists,
)
SYMREF = 'ref: '
def check_ref_format(refname):
"""Check if a refname is correctly formatted.
Implements all the same rules as git-check-ref-format[1].
[1] http://www.kernel.org/pub/software/scm/git/docs/git-check-ref-format.html
:param refname: The refname to check
:return: True if refname is valid, False otherwise
"""
# These could be combined into one big expression, but are listed separately
# to parallel [1].
if '/.' in refname or refname.startswith('.'):
return False
if '/' not in refname:
return False
if '..' in refname:
return False
for c in refname:
if ord(c) < 040 or c in '\177 ~^:?*[':
return False
if refname[-1] in '/.':
return False
if refname.endswith('.lock'):
return False
if '@{' in refname:
return False
if '\\' in refname:
return False
return True
class RefsContainer(object):
"""A container for refs."""
def set_symbolic_ref(self, name, other):
"""Make a ref point at another ref.
:param name: Name of the ref to set
:param other: Name of the ref to point at
"""
raise NotImplementedError(self.set_symbolic_ref)
def get_packed_refs(self):
"""Get contents of the packed-refs file.
:return: Dictionary mapping ref names to SHA1s
:note: Will return an empty dictionary when no packed-refs file is
present.
"""
raise NotImplementedError(self.get_packed_refs)
def get_peeled(self, name):
"""Return the cached peeled value of a ref, if available.
:param name: Name of the ref to peel
:return: The peeled value of the ref. If the ref is known not point to a
tag, this will be the SHA the ref refers to. If the ref may point to
a tag, but no cached information is available, None is returned.
"""
return None
def import_refs(self, base, other):
for name, value in other.iteritems():
self["%s/%s" % (base, name)] = value
def allkeys(self):
"""All refs present in this container."""
raise NotImplementedError(self.allkeys)
def keys(self, base=None):
"""Refs present in this container.
:param base: An optional base to return refs under.
:return: An unsorted set of valid refs in this container, including
packed refs.
"""
if base is not None:
return self.subkeys(base)
else:
return self.allkeys()
def subkeys(self, base):
"""Refs present in this container under a base.
:param base: The base to return refs under.
:return: A set of valid refs in this container under the base; the base
prefix is stripped from the ref names returned.
"""
keys = set()
base_len = len(base) + 1
for refname in self.allkeys():
if refname.startswith(base):
keys.add(refname[base_len:])
return keys
def as_dict(self, base=None):
"""Return the contents of this container as a dictionary.
"""
ret = {}
keys = self.keys(base)
if base is None:
base = ""
for key in keys:
try:
ret[key] = self[("%s/%s" % (base, key)).strip("/")]
except KeyError:
continue # Unable to resolve
return ret
def _check_refname(self, name):
"""Ensure a refname is valid and lives in refs or is HEAD.
HEAD is not a valid refname according to git-check-ref-format, but this
class needs to be able to touch HEAD. Also, check_ref_format expects
refnames without the leading 'refs/', but this class requires that
so it cannot touch anything outside the refs dir (or HEAD).
:param name: The name of the reference.
:raises KeyError: if a refname is not HEAD or is otherwise not valid.
"""
if name in ('HEAD', 'refs/stash'):
return
if not name.startswith('refs/') or not check_ref_format(name[5:]):
raise RefFormatError(name)
def read_ref(self, refname):
"""Read a reference without following any references.
:param refname: The name of the reference
:return: The contents of the ref file, or None if it does
not exist.
"""
contents = self.read_loose_ref(refname)
if not contents:
contents = self.get_packed_refs().get(refname, None)
return contents
def read_loose_ref(self, name):
"""Read a loose reference and return its contents.
:param name: the refname to read
:return: The contents of the ref file, or None if it does
not exist.
"""
raise NotImplementedError(self.read_loose_ref)
def _follow(self, name):
"""Follow a reference name.
:return: a tuple of (refname, sha), where refname is the name of the
last reference in the symbolic reference chain
"""
contents = SYMREF + name
depth = 0
while contents.startswith(SYMREF):
refname = contents[len(SYMREF):]
contents = self.read_ref(refname)
if not contents:
break
depth += 1
if depth > 5:
raise KeyError(name)
return refname, contents
def __contains__(self, refname):
if self.read_ref(refname):
return True
return False
def __getitem__(self, name):
"""Get the SHA1 for a reference name.
This method follows all symbolic references.
"""
_, sha = self._follow(name)
if sha is None:
raise KeyError(name)
return sha
def set_if_equals(self, name, old_ref, new_ref):
"""Set a refname to new_ref only if it currently equals old_ref.
This method follows all symbolic references if applicable for the
subclass, and can be used to perform an atomic compare-and-swap
operation.
:param name: The refname to set.
:param old_ref: The old sha the refname must refer to, or None to set
unconditionally.
:param new_ref: The new sha the refname will refer to.
:return: True if the set was successful, False otherwise.
"""
raise NotImplementedError(self.set_if_equals)
def add_if_new(self, name, ref):
"""Add a new reference only if it does not already exist."""
raise NotImplementedError(self.add_if_new)
def __setitem__(self, name, ref):
"""Set a reference name to point to the given SHA1.
This method follows all symbolic references if applicable for the
subclass.
:note: This method unconditionally overwrites the contents of a
reference. To update atomically only if the reference has not
changed, use set_if_equals().
:param name: The refname to set.
:param ref: The new sha the refname will refer to.
"""
self.set_if_equals(name, None, ref)
def remove_if_equals(self, name, old_ref):
"""Remove a refname only if it currently equals old_ref.
This method does not follow symbolic references, even if applicable for
the subclass. It can be used to perform an atomic compare-and-delete
operation.
:param name: The refname to delete.
:param old_ref: The old sha the refname must refer to, or None to delete
unconditionally.
:return: True if the delete was successful, False otherwise.
"""
raise NotImplementedError(self.remove_if_equals)
def __delitem__(self, name):
"""Remove a refname.
This method does not follow symbolic references, even if applicable for
the subclass.
:note: This method unconditionally deletes the contents of a reference.
To delete atomically only if the reference has not changed, use
remove_if_equals().
:param name: The refname to delete.
"""
self.remove_if_equals(name, None)
class DictRefsContainer(RefsContainer):
"""RefsContainer backed by a simple dict.
This container does not support symbolic or packed references and is not
threadsafe.
"""
def __init__(self, refs):
self._refs = refs
self._peeled = {}
def allkeys(self):
return self._refs.keys()
def read_loose_ref(self, name):
return self._refs.get(name, None)
def get_packed_refs(self):
return {}
def set_symbolic_ref(self, name, other):
self._refs[name] = SYMREF + other
def set_if_equals(self, name, old_ref, new_ref):
if old_ref is not None and self._refs.get(name, None) != old_ref:
return False
realname, _ = self._follow(name)
self._check_refname(realname)
self._refs[realname] = new_ref
return True
def add_if_new(self, name, ref):
if name in self._refs:
return False
self._refs[name] = ref
return True
def remove_if_equals(self, name, old_ref):
if old_ref is not None and self._refs.get(name, None) != old_ref:
return False
del self._refs[name]
return True
def get_peeled(self, name):
return self._peeled.get(name)
def _update(self, refs):
"""Update multiple refs; intended only for testing."""
# TODO(dborowitz): replace this with a public function that uses
# set_if_equal.
self._refs.update(refs)
def _update_peeled(self, peeled):
"""Update cached peeled refs; intended only for testing."""
self._peeled.update(peeled)
class InfoRefsContainer(RefsContainer):
"""Refs container that reads refs from a info/refs file."""
def __init__(self, f):
self._refs = {}
self._peeled = {}
for l in f.readlines():
sha, name = l.rstrip("\n").split("\t")
if name.endswith("^{}"):
name = name[:-3]
if not check_ref_format(name):
raise ValueError("invalid ref name '%s'" % name)
self._peeled[name] = sha
else:
if not check_ref_format(name):
raise ValueError("invalid ref name '%s'" % name)
self._refs[name] = sha
def allkeys(self):
return self._refs.keys()
def read_loose_ref(self, name):
return self._refs.get(name, None)
def get_packed_refs(self):
return {}
def get_peeled(self, name):
try:
return self._peeled[name]
except KeyError:
return self._refs[name]
class DiskRefsContainer(RefsContainer):
"""Refs container that reads refs from disk."""
def __init__(self, path):
self.path = path
self._packed_refs = None
self._peeled_refs = None
def __repr__(self):
return "%s(%r)" % (self.__class__.__name__, self.path)
def subkeys(self, base):
keys = set()
path = self.refpath(base)
for root, dirs, files in os.walk(path):
dir = root[len(path):].strip(os.path.sep).replace(os.path.sep, "/")
for filename in files:
refname = ("%s/%s" % (dir, filename)).strip("/")
# check_ref_format requires at least one /, so we prepend the
# base before calling it.
if check_ref_format("%s/%s" % (base, refname)):
keys.add(refname)
for key in self.get_packed_refs():
if key.startswith(base):
keys.add(key[len(base):].strip("/"))
return keys
def allkeys(self):
keys = set()
if os.path.exists(self.refpath("HEAD")):
keys.add("HEAD")
path = self.refpath("")
for root, dirs, files in os.walk(self.refpath("refs")):
dir = root[len(path):].strip(os.path.sep).replace(os.path.sep, "/")
for filename in files:
refname = ("%s/%s" % (dir, filename)).strip("/")
if check_ref_format(refname):
keys.add(refname)
keys.update(self.get_packed_refs())
return keys
def refpath(self, name):
"""Return the disk path of a ref.
"""
if os.path.sep != "/":
name = name.replace("/", os.path.sep)
return os.path.join(self.path, name)
def get_packed_refs(self):
"""Get contents of the packed-refs file.
:return: Dictionary mapping ref names to SHA1s
:note: Will return an empty dictionary when no packed-refs file is
present.
"""
# TODO: invalidate the cache on repacking
if self._packed_refs is None:
# set both to empty because we want _peeled_refs to be
# None if and only if _packed_refs is also None.
self._packed_refs = {}
self._peeled_refs = {}
path = os.path.join(self.path, 'packed-refs')
try:
f = GitFile(path, 'rb')
except IOError, e:
if e.errno == errno.ENOENT:
return {}
raise
try:
first_line = iter(f).next().rstrip()
if (first_line.startswith("# pack-refs") and " peeled" in
first_line):
for sha, name, peeled in read_packed_refs_with_peeled(f):
self._packed_refs[name] = sha
if peeled:
self._peeled_refs[name] = peeled
else:
f.seek(0)
for sha, name in read_packed_refs(f):
self._packed_refs[name] = sha
finally:
f.close()
return self._packed_refs
def get_peeled(self, name):
"""Return the cached peeled value of a ref, if available.
:param name: Name of the ref to peel
:return: The peeled value of the ref. If the ref is known not point to a
tag, this will be the SHA the ref refers to. If the ref may point to
a tag, but no cached information is available, None is returned.
"""
self.get_packed_refs()
if self._peeled_refs is None or name not in self._packed_refs:
# No cache: no peeled refs were read, or this ref is loose
return None
if name in self._peeled_refs:
return self._peeled_refs[name]
else:
# Known not peelable
return self[name]
def read_loose_ref(self, name):
"""Read a reference file and return its contents.
If the reference file a symbolic reference, only read the first line of
the file. Otherwise, only read the first 40 bytes.
:param name: the refname to read, relative to refpath
:return: The contents of the ref file, or None if the file does not
exist.
:raises IOError: if any other error occurs
"""
filename = self.refpath(name)
try:
f = GitFile(filename, 'rb')
try:
header = f.read(len(SYMREF))
if header == SYMREF:
# Read only the first line
return header + iter(f).next().rstrip("\r\n")
else:
# Read only the first 40 bytes
return header + f.read(40 - len(SYMREF))
finally:
f.close()
except IOError, e:
if e.errno == errno.ENOENT:
return None
raise
def _remove_packed_ref(self, name):
if self._packed_refs is None:
return
filename = os.path.join(self.path, 'packed-refs')
# reread cached refs from disk, while holding the lock
f = GitFile(filename, 'wb')
try:
self._packed_refs = None
self.get_packed_refs()
if name not in self._packed_refs:
return
del self._packed_refs[name]
if name in self._peeled_refs:
del self._peeled_refs[name]
write_packed_refs(f, self._packed_refs, self._peeled_refs)
f.close()
finally:
f.abort()
def set_symbolic_ref(self, name, other):
"""Make a ref point at another ref.
:param name: Name of the ref to set
:param other: Name of the ref to point at
"""
self._check_refname(name)
self._check_refname(other)
filename = self.refpath(name)
try:
f = GitFile(filename, 'wb')
try:
f.write(SYMREF + other + '\n')
except (IOError, OSError):
f.abort()
raise
finally:
f.close()
def set_if_equals(self, name, old_ref, new_ref):
"""Set a refname to new_ref only if it currently equals old_ref.
This method follows all symbolic references, and can be used to perform
an atomic compare-and-swap operation.
:param name: The refname to set.
:param old_ref: The old sha the refname must refer to, or None to set
unconditionally.
:param new_ref: The new sha the refname will refer to.
:return: True if the set was successful, False otherwise.
"""
self._check_refname(name)
try:
realname, _ = self._follow(name)
except KeyError:
realname = name
filename = self.refpath(realname)
ensure_dir_exists(os.path.dirname(filename))
f = GitFile(filename, 'wb')
try:
if old_ref is not None:
try:
# read again while holding the lock
orig_ref = self.read_loose_ref(realname)
if orig_ref is None:
orig_ref = self.get_packed_refs().get(realname, None)
if orig_ref != old_ref:
f.abort()
return False
except (OSError, IOError):
f.abort()
raise
try:
f.write(new_ref + "\n")
except (OSError, IOError):
f.abort()
raise
finally:
f.close()
return True
def add_if_new(self, name, ref):
"""Add a new reference only if it does not already exist.
This method follows symrefs, and only ensures that the last ref in the
chain does not exist.
:param name: The refname to set.
:param ref: The new sha the refname will refer to.
:return: True if the add was successful, False otherwise.
"""
try:
realname, contents = self._follow(name)
if contents is not None:
return False
except KeyError:
realname = name
self._check_refname(realname)
filename = self.refpath(realname)
ensure_dir_exists(os.path.dirname(filename))
f = GitFile(filename, 'wb')
try:
if os.path.exists(filename) or name in self.get_packed_refs():
f.abort()
return False
try:
f.write(ref + "\n")
except (OSError, IOError):
f.abort()
raise
finally:
f.close()
return True
def remove_if_equals(self, name, old_ref):
"""Remove a refname only if it currently equals old_ref.
This method does not follow symbolic references. It can be used to
perform an atomic compare-and-delete operation.
:param name: The refname to delete.
:param old_ref: The old sha the refname must refer to, or None to delete
unconditionally.
:return: True if the delete was successful, False otherwise.
"""
self._check_refname(name)
filename = self.refpath(name)
ensure_dir_exists(os.path.dirname(filename))
f = GitFile(filename, 'wb')
try:
if old_ref is not None:
orig_ref = self.read_loose_ref(name)
if orig_ref is None:
orig_ref = self.get_packed_refs().get(name, None)
if orig_ref != old_ref:
return False
# may only be packed
try:
os.remove(filename)
except OSError, e:
if e.errno != errno.ENOENT:
raise
self._remove_packed_ref(name)
finally:
# never write, we just wanted the lock
f.abort()
return True
def _split_ref_line(line):
"""Split a single ref line into a tuple of SHA1 and name."""
fields = line.rstrip("\n").split(" ")
if len(fields) != 2:
raise PackedRefsException("invalid ref line '%s'" % line)
sha, name = fields
try:
hex_to_sha(sha)
except (AssertionError, TypeError), e:
raise PackedRefsException(e)
if not check_ref_format(name):
raise PackedRefsException("invalid ref name '%s'" % name)
return (sha, name)
def read_packed_refs(f):
"""Read a packed refs file.
:param f: file-like object to read from
:return: Iterator over tuples with SHA1s and ref names.
"""
for l in f:
if l[0] == "#":
# Comment
continue
if l[0] == "^":
raise PackedRefsException(
"found peeled ref in packed-refs without peeled")
yield _split_ref_line(l)
def read_packed_refs_with_peeled(f):
"""Read a packed refs file including peeled refs.
Assumes the "# pack-refs with: peeled" line was already read. Yields tuples
with ref names, SHA1s, and peeled SHA1s (or None).
:param f: file-like object to read from, seek'ed to the second line
"""
last = None
for l in f:
if l[0] == "#":
continue
l = l.rstrip("\r\n")
if l[0] == "^":
if not last:
raise PackedRefsException("unexpected peeled ref line")
try:
hex_to_sha(l[1:])
except (AssertionError, TypeError), e:
raise PackedRefsException(e)
sha, name = _split_ref_line(last)
last = None
yield (sha, name, l[1:])
else:
if last:
sha, name = _split_ref_line(last)
yield (sha, name, None)
last = l
if last:
sha, name = _split_ref_line(last)
yield (sha, name, None)
def write_packed_refs(f, packed_refs, peeled_refs=None):
"""Write a packed refs file.
:param f: empty file-like object to write to
:param packed_refs: dict of refname to sha of packed refs to write
:param peeled_refs: dict of refname to peeled value of sha
"""
if peeled_refs is None:
peeled_refs = {}
else:
f.write('# pack-refs with: peeled\n')
for refname in sorted(packed_refs.iterkeys()):
f.write('%s %s\n' % (packed_refs[refname], refname))
if refname in peeled_refs:
f.write('^%s\n' % peeled_refs[refname])
def read_info_refs(f):
ret = {}
for l in f.readlines():
(sha, name) = l.rstrip("\r\n").split("\t", 1)
ret[name] = sha
return ret
def write_info_refs(refs, store):
"""Generate info refs."""
for name, sha in sorted(refs.items()):
# get_refs() includes HEAD as a special case, but we don't want to
# advertise it
if name == 'HEAD':
continue
try:
o = store[sha]
except KeyError:
continue
peeled = store.peel_sha(sha)
yield '%s\t%s\n' % (o.id, name)
if o.id != peeled.id:
yield '%s\t%s^{}\n' % (peeled.id, name)
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