view tests/test-git-import.out @ 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%.

% new file
applying patch from stdin
0:ae3ee40d2079
% new empty file
applying patch from stdin
1:ab199dc869b5
empty
% chmod +x
applying patch from stdin
2:3a34410f282e
% copy
applying patch from stdin
3:37bacb7ca14d
a
a
% rename
applying patch from stdin
4:47b81a94361d
copyx
empty
new
rename
% delete
applying patch from stdin
5:d9b001d98336
empty
new
rename
% regular diff
applying patch from stdin
6:ebe901e7576b
% copy and modify
applying patch from stdin
7:18f368958ecd
a
a
b
a
a
% rename and modify
applying patch from stdin
8:c32b0d7e6f44
a
a
b
c
a
% one file renamed multiple times
applying patch from stdin
9:034a6bf95330
9 rename2 rename3 rename3-2 / rename3 (rename2)rename3-2 (rename2)
rename3
rename3-2
a
a
b
c
a

a
a
b
c
a
% binary files and regular patch hunks
applying patch from stdin
11:c39bce63e786
foo
045c85ba38952325e126c70962cc0f9d9077bc67 644   binary
% many binary files
applying patch from stdin
12:30b530085242
045c85ba38952325e126c70962cc0f9d9077bc67 644   mbinary1
a874b471193996e7cb034bb301cac7bdaf3e3f46 644   mbinary2
% filenames with spaces
applying patch from stdin
13:04750ef42fb3
foo
% copy then modify the original file
applying patch from stdin
14:c4cd9cdeaa74
foo