view tests/test-dumprevlog.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%.

% prepare repo-a
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 3 changesets, 3 total revisions

% dumping revlog of file a to stdout
file: .hg/store/data/a.i
node: 183d2312b35066fb6b3b449b84efc370d50993d0
linkrev: 0
parents: 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
length: 15
-start-
this is file a

-end-
node: b1047953b6e6b633c0d8197eaa5116fbdfd3095b
linkrev: 1
parents: 183d2312b35066fb6b3b449b84efc370d50993d0 0000000000000000000000000000000000000000
length: 32
-start-
this is file a
adding to file a

-end-
node: 8c4fd1f7129b8cdec6c7f58bf48fb5237a4030c1
linkrev: 2
parents: b1047953b6e6b633c0d8197eaa5116fbdfd3095b 0000000000000000000000000000000000000000
length: 54
-start-
this is file a
adding to file a
adding more to file a

-end-
% dumprevlog done

% dump all revlogs to file repo.dump

% undumping into repo-b
.hg/store/00changelog.i
.hg/store/00manifest.i
.hg/store/data/a.i
% undumping done

% clone --pull repo-b repo-c to rebuild fncache
requesting all changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 1 files

% verify repo-c
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 3 changesets, 3 total revisions

% comparing repos
comparing with repo-a
searching for changes
no changes found
comparing with repo-c
searching for changes
no changes found