annotate tests/test-parseindex @ 11769:ca6cebd8734e stable

dirstate: ignore symlinks when fs cannot handle them (issue1888)

When the filesystem cannot handle the executable bit, we currently
ignore it completely when looking for modified files. Similarly, it is
impossible to set or clear the bit when the filesystem ignores it.

This patch makes Mercurial treat symbolic links the same way.

Symlinks are a little different since they manifest themselves as
small files containing a filename (the symlink target). On Windows,
these files show up as regular files, and on Linux and Mac they show
up as real symlinks.

Issue1888 presents a case where the symlink files are better ignored
from the Windows side. A Linux client creates symlinks in a working
copy which is shared over a network between Linux and Windows clients.

The Samba server is helpful and defererences the symlink when the
Windows client looks at it. This means that Mercurial on the Windows
side sees file content instead of a file name in the symlink, and
hence flags the link as modified. Ignoring the change would be much
more helpful, similarly to how Mercurial does not report any changes
when executable bits are ignored in a checkout on Windows.

An initial checkout of a symbolic link on a file system that cannot
handle symbolic links will still result in a regular file containing
the target file name as its content. Sharing such a checkout with a
Linux client will not turn the file into a symlink automatically, but
'hg revert' can fix that. After the revert, the Windows client will
see the correct file content (provided by the Samba server when it
follows the link on the Linux side) and otherwise ignore the change.

Running 'hg perfstatus' 10 times gives these results:

  Before:          After:
  min: 0.544703    min: 0.546549
  med: 0.547592    med: 0.548881
  avg: 0.549146    avg: 0.548549
  max: 0.564112    max: 0.551504

The median time is increased about 0.24%.

#!/bin/sh
#
# revlog.parseindex must be able to parse the index file even if
# an index entry is split between two 64k blocks.  The ideal test
# would be to create an index file with inline data where
# 64k < size < 64k + 64 (64k is the size of the read buffer, 64 is
# the size of an index entry) and with an index entry starting right
# before the 64k block boundary, and try to read it.
#
# We approximate that by reducing the read buffer to 1 byte.
#

hg init a
cd a
echo abc > foo
hg add foo
hg commit -m 'add foo' -d '1000000 0'

echo >> foo
hg commit -m 'change foo' -d '1000001 0'
hg log -r 0:

cat >> test.py << EOF
from mercurial import changelog, util
from mercurial.node import *

class singlebyteread(object):
    def __init__(self, real):
        self.real = real

    def read(self, size=-1):
        if size == 65536:
            size = 1
        return self.real.read(size)

    def __getattr__(self, key):
        return getattr(self.real, key)

def opener(*args):
    o = util.opener(*args)
    def wrapper(*a):
        f = o(*a)
        return singlebyteread(f)
    return wrapper

cl = changelog.changelog(opener('.hg/store'))
print len(cl), 'revisions:'
for r in cl:
    print short(cl.node(r))
EOF

python test.py