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%.
% no diff if hardlink
% init
adding foo to series file
applying foo
now at: foo
adding bar to series file
applying bar
now at: bar
430ed4828a74fa4047bc816a25500f7472ab4bfe:foo
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c:bar
%
foo
bar
%%%
430ed4828a74fa4047bc816a25500f7472ab4bfe:foo
%
foo
patch foo finalized without changeset message
patch bar finalized without changeset message
%%%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c foo
430ed4828a74fa4047bc816a25500f7472ab4bfe bar
%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c lfoo
430ed4828a74fa4047bc816a25500f7472ab4bfe lbar
%%%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c foo
%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c lfoo