tests/test-diff-upgrade

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

echo "[extensions]" >> $HGRCPATH
echo "autodiff=$TESTDIR/autodiff.py" >> $HGRCPATH
echo "[diff]" >> $HGRCPATH
echo "nodates=1" >> $HGRCPATH

hg init repo
cd repo
echo '% make a combination of new, changed and deleted file'
echo regular > regular
echo rmregular > rmregular
touch rmempty
echo exec > exec
chmod +x exec
echo rmexec > rmexec
chmod +x rmexec
echo setexec > setexec
echo unsetexec > unsetexec
chmod +x unsetexec
echo binary > binary
python -c "file('rmbinary', 'wb').write('\0')"
hg ci -Am addfiles
echo regular >> regular
echo newregular >> newregular
rm rmempty
touch newempty
rm rmregular
echo exec >> exec
echo newexec > newexec
chmod +x newexec
rm rmexec
chmod +x setexec
chmod -x unsetexec
python -c "file('binary', 'wb').write('\0\0')"
python -c "file('newbinary', 'wb').write('\0')"
rm rmbinary
hg addremove

echo '% git=no: regular diff for all files'
hg autodiff --git=no

echo '% git=no: git diff for single regular file'
hg autodiff --git=yes regular

echo '% git=auto: regular diff for regular files and removals'
hg autodiff --git=auto regular newregular rmregular rmbinary rmexec

for f in exec newexec setexec unsetexec binary newbinary newempty rmempty; do
    echo '% git=auto: git diff for' $f
    hg autodiff --git=auto $f
done

echo '% git=warn: regular diff with data loss warnings'
hg autodiff --git=warn

echo '% git=abort: fail on execute bit change'
hg autodiff --git=abort regular setexec

echo '% git=abort: succeed on regular file'
hg autodiff --git=abort regular

cd ..