view mercurial/httprangereader.py @ 5378:8a2915f57dfc

convert: add a mode where mercurial_sink skips empty revisions.

The getchanges function of some converter_source classes can return
some false positives.  I.e. they sometimes claim that a file "foo"
was changed in some revision, even though its contents are still the
same.

convert_svn is particularly bad, but I think this can also happen with
convert_cvs and, at least in theory, with mercurial_source.

For regular conversions this is not really a problem - as long as
getfile returns the right contents, we'll get a converted revision
with the right contents.  But when we use --filemap, this could lead
to superfluous revisions being converted.

Instead of fixing every converter_source, I decided to change
mercurial_sink to work around this problem.

When --filemap is used, we're interested only in revisions that touch
some specific files.  If a revision doesn't change any of these files,
then we're not interested in it (at least for revisions with a single
parent; merges are special).

For mercurial_sink, we abuse this property and rollback a commit if
the manifest text hasn't changed.  This avoids duplicating the logic
from localrepo.filecommit to detect unchanged files.

# httprangereader.py - just what it says
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import byterange, urllib2

class httprangereader(object):
    def __init__(self, url):
        self.url = url
        self.pos = 0
    def seek(self, pos):
        self.pos = pos
    def read(self, bytes=None):
        opener = urllib2.build_opener(byterange.HTTPRangeHandler())
        urllib2.install_opener(opener)
        req = urllib2.Request(self.url)
        end = ''
        if bytes:
            end = self.pos + bytes - 1
        req.add_header('Range', 'bytes=%d-%s' % (self.pos, end))
        f = urllib2.urlopen(req)
        data = f.read()
        if bytes:
            data = data[:bytes]
        return data