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%.