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httppeer: detect redirect to URL without query string (issue5860)...
httppeer: detect redirect to URL without query string (issue5860) 197d10e157ce subtly changed the HTTP peer's handling of HTTP redirects. Before that changeset, we instantiated an HTTP peer instance and performed the capabilities lookup with that instance. The old code had the following relevant properties: 1) The HTTP request layer would automatically follow HTTP redirects. 2) An encountered HTTP redirect would update a peer instance variable pointing to the repo URL. 3) The peer would automagically perform a "capabilities" command request if a caller requested capabilities but capabilities were not yet defined. The first HTTP request issued by a peer is for ?cmd=capabilities. If the server responds with an HTTP redirect to a ?cmd=capabilities URL, the HTTP request layer automatically followed it, retrieved a valid capabilities response, and the peer's base URL was updated automatically so subsequent requests used the proper URL. In other words, things "just worked." In the case where the server redirected to a URL without the ?cmd=capabilities query string, the HTTP request layer would follow the redirect and likely encounter HTML. The peer's base URL would be updated and the unexpected Content-Type would raise a RepoError. We would catch RepoError and immediately call between() (testing the case for pre 0.9.1 servers not supporting the "capabilities" command). e.g. try: inst._fetchcaps() except error.RepoError: inst.between([(nullid, nullid)]) between() would eventually call into _callstream(). And _callstream() made a call to self.capable('httpheader'). capable() would call self.capabilities(), which would see that no capabilities were set (because HTML was returned for that request) and call the "capabilities" command to fetch capabilities. Because the base URL had been updated from the redirect, this 2nd "capabilities" command would succeed and the client would immediately call "between," which would also succeed. The legacy handshake succeeded. Only because "capabilities" was successfully executed as a side effect did the peer recognize that it was talking to a modern server. In other words, this all appeared to work accidentally. After 197d10e157ce, we stopped calling the "capabilities" command on the peer instance. Instead, we made the request via a low-level opener, detected the redirect as part of response handling code, and passed the redirected URL into the constructed peer instance. For cases where the redirected URL included the query string, this "just worked." But for cases where the redirected URL stripped the query string, we threw RepoError and because we removed the "between" handshake fallback, we fell through to the "is a static HTTP repo" check and performed an HTTP request for .hg/requires. While 197d10e157ce was marked as backwards incompatible, the only intended backwards incompatible behavior was not performing the "between" fallback. It was not realized that the "between" command had the side-effect of recovering from an errant redirect that dropped the query string. This commit restores the previous behavior and allows clients to handle a redirect that drops the query string. In the case where the request is redirected and the query string is dropped, we raise a special case of RepoError. We then catch this special exception in the handshake code and perform another "capabilities" request against the redirected URL. If that works, all is well. Otherwise, we fall back to the "is a static HTTP repo" check. The new code is arguably better than before 197d10e157ce, as it is explicit about the expected behavior and we avoid performing a "between" request, saving a server round trip. Differential Revision: https://phab.mercurial-scm.org/D3433

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narrowrevlog.py
80 lines | 3.0 KiB | text/x-python | PythonLexer
# narrowrevlog.py - revlog storing irrelevant nodes as "ellipsis" nodes
#
# Copyright 2017 Google, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
from mercurial import (
revlog,
util,
)
def readtransform(self, text):
return text, False
def writetransform(self, text):
return text, False
def rawtransform(self, text):
return False
revlog.addflagprocessor(revlog.REVIDX_ELLIPSIS,
(readtransform, writetransform, rawtransform))
def setup():
# We just wanted to add the flag processor, which is done at module
# load time.
pass
def makenarrowfilelog(fl, narrowmatch):
class narrowfilelog(fl.__class__):
def renamed(self, node):
# Renames that come from outside the narrowspec are
# problematic at least for git-diffs, because we lack the
# base text for the rename. This logic was introduced in
# 3cd72b1 of narrowhg (authored by martinvonz, reviewed by
# adgar), but that revision doesn't have any additional
# commentary on what problems we can encounter.
m = super(narrowfilelog, self).renamed(node)
if m and not narrowmatch(m[0]):
return None
return m
def size(self, rev):
# We take advantage of the fact that remotefilelog
# lacks a node() method to just skip the
# rename-checking logic when on remotefilelog. This
# might be incorrect on other non-revlog-based storage
# engines, but for now this seems to be fine.
#
# TODO: when remotefilelog is in core, improve this to
# explicitly look for remotefilelog instead of cheating
# with a hasattr check.
if util.safehasattr(self, 'node'):
node = self.node(rev)
# Because renamed() is overridden above to
# sometimes return None even if there is metadata
# in the revlog, size can be incorrect for
# copies/renames, so we need to make sure we call
# the super class's implementation of renamed()
# for the purpose of size calculation.
if super(narrowfilelog, self).renamed(node):
return len(self.read(node))
return super(narrowfilelog, self).size(rev)
def cmp(self, node, text):
different = super(narrowfilelog, self).cmp(node, text)
if different:
# Similar to size() above, if the file was copied from
# a file outside the narrowspec, the super class's
# would have returned True because we tricked it into
# thinking that the file was not renamed.
if super(narrowfilelog, self).renamed(node):
t2 = self.read(node)
return t2 != text
return different
fl.__class__ = narrowfilelog