/usr/lib/python2.7/dist-packages/hgext/git/hg2git.py is in mercurial-git 0.8.5-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# repositories to Git repositories. Code in this file is meant to be a generic
# library and should be usable outside the context of hg-git or an hg command.
import os
import stat
import dulwich.objects as dulobjs
from mercurial import (
util as hgutil,
)
import compat
import util
def parse_subrepos(ctx):
sub = util.OrderedDict()
if '.hgsub' in ctx:
sub = util.parse_hgsub(ctx['.hgsub'].data().splitlines())
substate = util.OrderedDict()
if '.hgsubstate' in ctx:
substate = util.parse_hgsubstate(
ctx['.hgsubstate'].data().splitlines())
return sub, substate
def audit_git_path(ui, path):
r"""Check for path components that case-fold to .git.
>>> class fakeui(object):
... def configbool(*args):
... return False
... def warn(self, s):
... print s
>>> u = fakeui()
>>> audit_git_path(u, 'foo/git~100/wat')
warning: path 'foo/git~100/wat' contains a potentially dangerous path component.
It may not be legal to check out in Git.
It may also be rejected by some git server configurations.
<BLANKLINE>
>>> audit_git_path(u, u'foo/.gi\u200ct'.encode('utf-8'))
warning: path 'foo/.gi\xe2\x80\x8ct' contains a potentially dangerous path component.
It may not be legal to check out in Git.
It may also be rejected by some git server configurations.
<BLANKLINE>
>>> audit_git_path(u, 'this/is/safe')
"""
dangerous = False
for c in path.split(os.path.sep):
if compat.hfsignoreclean(c) == '.git':
dangerous = True
break
elif '~' in c:
base, tail = c.split('~', 1)
if tail.isdigit() and base.upper().startswith('GIT'):
dangerous = True
break
if dangerous:
if ui.configbool('git', 'blockdotgit', True):
raise hgutil.Abort(
('Refusing to export likely-dangerous path %r' % path),
hint=("If you need to continue, read about CVE-2014-9390 and "
"then set '[git] blockdotgit = false' in your hgrc."))
ui.warn('warning: path %r contains a potentially dangerous path '
'component.\n'
'It may not be legal to check out in Git.\n'
'It may also be rejected by some git server configurations.\n'
% path)
class IncrementalChangesetExporter(object):
"""Incrementally export Mercurial changesets to Git trees.
The purpose of this class is to facilitate Git tree export that is more
optimal than brute force.
A "dumb" implementations of Mercurial to Git export would iterate over
every file present in a Mercurial changeset and would convert each to
a Git blob and then conditionally add it to a Git repository if it didn't
yet exist. This is suboptimal because the overhead associated with
obtaining every file's raw content and converting it to a Git blob is
not trivial!
This class works around the suboptimality of brute force export by
leveraging the information stored in Mercurial - the knowledge of what
changed between changesets - to only export Git objects corresponding to
changes in Mercurial. In the context of converting Mercurial repositories
to Git repositories, we only export objects Git (possibly) hasn't seen yet.
This prevents a lot of redundant work and is thus faster.
Callers instantiate an instance of this class against a mercurial.localrepo
instance. They then associate it with a specific changesets by calling
update_changeset(). On each call to update_changeset(), the instance
computes the difference between the current and new changesets and emits
Git objects that haven't yet been encountered during the lifetime of the
class instance. In other words, it expresses Mercurial changeset deltas in
terms of Git objects. Callers then (usually) take this set of Git objects
and add them to the Git repository.
This class only emits Git blobs and trees, not commits.
The tree calculation part of this class is essentially a reimplementation
of dulwich.index.commit_tree. However, since our implementation reuses
Tree instances and only recalculates SHA-1 when things change, we are
more efficient.
"""
def __init__(self, hg_repo, start_ctx, git_store, git_commit):
"""Create an instance against a mercurial.localrepo.
start_ctx: the context for a Mercurial commit that has a Git
equivalent, passed in as git_commit. The incremental
computation will be started from this commit.
git_store: the Git object store the commit comes from.
start_ctx can be repo[nullid], in which case git_commit should be None.
"""
self._hg = hg_repo
# Our current revision's context.
self._ctx = start_ctx
# Path to dulwich.objects.Tree.
self._init_dirs(git_store, git_commit)
# Mercurial file nodeid to Git blob SHA-1. Used to prevent redundant
# blob calculation.
self._blob_cache = {}
def _init_dirs(self, store, commit):
"""Initialize self._dirs for a Git object store and commit."""
self._dirs = {}
if commit is None:
return
dirkind = stat.S_IFDIR
# depth-first order, chosen arbitrarily
todo = [('', store[commit.tree])]
while todo:
path, tree = todo.pop()
self._dirs[path] = tree
for entry in tree.iteritems():
if entry.mode == dirkind:
if path == '':
newpath = entry.path
else:
newpath = path + '/' + entry.path
todo.append((newpath, store[entry.sha]))
@property
def root_tree_sha(self):
"""The SHA-1 of the root Git tree.
This is needed to construct a Git commit object.
"""
return self._dirs[''].id
def update_changeset(self, newctx):
"""Set the tree to track a new Mercurial changeset.
This is a generator of 2-tuples. The first item in each tuple is a
dulwich object, either a Blob or a Tree. The second item is the
corresponding Mercurial nodeid for the item, if any. Only blobs will
have nodeids. Trees do not correspond to a specific nodeid, so it does
not make sense to emit a nodeid for them.
When exporting trees from Mercurial, callers typically write the
returned dulwich object to the Git repo via the store's add_object().
Some emitted objects may already exist in the Git repository. This
class does not know about the Git repository, so it's up to the caller
to conditionally add the object, etc.
Emitted objects are those that have changed since the last call to
update_changeset. If this is the first call to update_chanageset, all
objects in the tree are emitted.
"""
# Our general strategy is to accumulate dulwich.objects.Blob and
# dulwich.objects.Tree instances for the current Mercurial changeset.
# We do this incremental by iterating over the Mercurial-reported
# changeset delta. We rely on the behavior of Mercurial to lazy
# calculate a Tree's SHA-1 when we modify it. This is critical to
# performance.
# In theory we should be able to look at changectx.files(). This is
# *much* faster. However, it may not be accurate, especially with older
# repositories, which may not record things like deleted files
# explicitly in the manifest (which is where files() gets its data).
# The only reliable way to get the full set of changes is by looking at
# the full manifest. And, the easy way to compare two manifests is
# localrepo.status().
modified, added, removed = self._hg.status(self._ctx, newctx)[0:3]
# We track which directories/trees have modified in this update and we
# only export those.
dirty_trees = set()
subadded, subremoved = [], []
for s in modified, added, removed:
if '.hgsub' in s or '.hgsubstate' in s:
subadded, subremoved = self._handle_subrepos(newctx)
break
# We first process subrepo and file removals so we can prune dead
# trees.
for path in subremoved:
self._remove_path(path, dirty_trees)
for path in removed:
if path == '.hgsubstate' or path == '.hgsub':
continue
self._remove_path(path, dirty_trees)
for path, sha in subadded:
d = os.path.dirname(path)
tree = self._dirs.setdefault(d, dulobjs.Tree())
dirty_trees.add(d)
tree.add(os.path.basename(path), dulobjs.S_IFGITLINK, sha)
# For every file that changed or was added, we need to calculate the
# corresponding Git blob and its tree entry. We emit the blob
# immediately and update trees to be aware of its presence.
for path in set(modified) | set(added):
audit_git_path(self._hg.ui, path)
if path == '.hgsubstate' or path == '.hgsub':
continue
d = os.path.dirname(path)
tree = self._dirs.setdefault(d, dulobjs.Tree())
dirty_trees.add(d)
fctx = newctx[path]
func = IncrementalChangesetExporter.tree_entry
entry, blob = func(fctx, self._blob_cache)
if blob is not None:
yield (blob, fctx.filenode())
tree.add(*entry)
# Now that all the trees represent the current changeset, recalculate
# the tree IDs and emit them. Note that we wait until now to calculate
# tree SHA-1s. This is an important difference between us and
# dulwich.index.commit_tree(), which builds new Tree instances for each
# series of blobs.
for obj in self._populate_tree_entries(dirty_trees):
yield (obj, None)
self._ctx = newctx
def _remove_path(self, path, dirty_trees):
"""Remove a path (file or git link) from the current changeset.
If the tree containing this path is empty, it might be removed."""
d = os.path.dirname(path)
tree = self._dirs.get(d, dulobjs.Tree())
del tree[os.path.basename(path)]
dirty_trees.add(d)
# If removing this file made the tree empty, we should delete this
# tree. This could result in parent trees losing their only child
# and so on.
if not len(tree):
self._remove_tree(d)
else:
self._dirs[d] = tree
def _remove_tree(self, path):
"""Remove a (presumably empty) tree from the current changeset.
A now-empty tree may be the only child of its parent. So, we traverse
up the chain to the root tree, deleting any empty trees along the way.
"""
try:
del self._dirs[path]
except KeyError:
return
# Now we traverse up to the parent and delete any references.
if path == '':
return
basename = os.path.basename(path)
parent = os.path.dirname(path)
while True:
tree = self._dirs.get(parent, None)
# No parent entry. Nothing to remove or update.
if tree is None:
return
try:
del tree[basename]
except KeyError:
return
if len(tree):
return
# The parent tree is empty. Se, we can delete it.
del self._dirs[parent]
if parent == '':
return
basename = os.path.basename(parent)
parent = os.path.dirname(parent)
def _populate_tree_entries(self, dirty_trees):
self._dirs.setdefault('', dulobjs.Tree())
# Fill in missing directories.
for path in self._dirs.keys():
parent = os.path.dirname(path)
while parent != '':
parent_tree = self._dirs.get(parent, None)
if parent_tree is not None:
break
self._dirs[parent] = dulobjs.Tree()
parent = os.path.dirname(parent)
for dirty in list(dirty_trees):
parent = os.path.dirname(dirty)
while parent != '':
if parent in dirty_trees:
break
dirty_trees.add(parent)
parent = os.path.dirname(parent)
# The root tree is always dirty but doesn't always get updated.
dirty_trees.add('')
# We only need to recalculate and export dirty trees.
for d in sorted(dirty_trees, key=len, reverse=True):
# Only happens for deleted directories.
try:
tree = self._dirs[d]
except KeyError:
continue
yield tree
if d == '':
continue
parent_tree = self._dirs[os.path.dirname(d)]
# Accessing the tree's ID is what triggers SHA-1 calculation and is
# the expensive part (at least if the tree has been modified since
# the last time we retrieved its ID). Also, assigning an entry to a
# tree (even if it already exists) invalidates the existing tree
# and incurs SHA-1 recalculation. So, it's in our interest to avoid
# invalidating trees. Since we only update the entries of dirty
# trees, this should hold true.
parent_tree[os.path.basename(d)] = (stat.S_IFDIR, tree.id)
def _handle_subrepos(self, newctx):
sub, substate = parse_subrepos(self._ctx)
newsub, newsubstate = parse_subrepos(newctx)
# For each path, the logic is described by the following table. 'no'
# stands for 'the subrepo doesn't exist', 'git' stands for 'git
# subrepo', and 'hg' stands for 'hg or other subrepo'.
#
# old new | action
# * git | link (1)
# git hg | delete (2)
# git no | delete (3)
#
# All other combinations are 'do nothing'.
#
# git links without corresponding submodule paths are stored as
# subrepos with a substate but without an entry in .hgsub.
# 'added' is both modified and added
added, removed = [], []
def isgit(sub, path):
return path not in sub or sub[path].startswith('[git]')
for path, sha in substate.iteritems():
if not isgit(sub, path):
# old = hg -- will be handled in next loop
continue
# old = git
if path not in newsubstate or not isgit(newsub, path):
# new = hg or no, case (2) or (3)
removed.append(path)
for path, sha in newsubstate.iteritems():
if not isgit(newsub, path):
# new = hg or no; the only cases we care about are handled
# above
continue
# case (1)
added.append((path, sha))
return added, removed
@staticmethod
def tree_entry(fctx, blob_cache):
"""Compute a dulwich TreeEntry from a filectx.
A side effect is the TreeEntry is stored in the passed cache.
Returns a 2-tuple of (dulwich.objects.TreeEntry, dulwich.objects.Blob).
"""
blob_id = blob_cache.get(fctx.filenode(), None)
blob = None
if blob_id is None:
blob = dulobjs.Blob.from_string(fctx.data())
blob_id = blob.id
blob_cache[fctx.filenode()] = blob_id
flags = fctx.flags()
if 'l' in flags:
mode = 0120000
elif 'x' in flags:
mode = 0100755
else:
mode = 0100644
return (dulobjs.TreeEntry(os.path.basename(fctx.path()), mode,
blob_id), blob)
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