Copying and moving a symlink to another FS fails if the target is relative

[Saulius Krasuckas]

This happens on a recently updated MSYS2:

$ uname -a
MSYS_NT-10.0-19044 DESKTOP-O7JE7JE 3.4.10.x86_64 2023-12-22 10:06 UTC x86_64 Msys

IOW, if after the operation a symlink would become broken (by target being relative), it won't cross the FS boundaries:

DEST_DIR=/tmp/destination
export DEST_DIR

echo The content > original
ln -sv original symlink-1
ln -sv original symlink-2
mkdir -pv ${DEST_DIR}

cp -Pv symlink-1 ${DEST_DIR}
mv -v symlink-2 ${DEST_DIR}

Actual output:

'symlink-1' -> 'original'
'symlink-2' -> 'original'
mkdir: created directory '/tmp/destination'
'symlink-1' -> '/tmp/destination/symlink-1'
cp: cannot create symbolic link '/tmp/destination/symlink-1': No such file or directory
copied 'symlink-2' -> '/tmp/destination/symlink-2'
mv: cannot create symbolic link '/tmp/destination/symlink-2': No such file or directory

A bit more verbose testing: https://asciinema.org/a/632681

If the destination dir is on the same FS, only copying is broken. Moving the symlink works fine:

'symlink-1' -> 'original'
'symlink-2' -> 'original'
mkdir: created directory '/tmp/destination'
'symlink-1' -> '/tmp/destination/symlink-1'
cp: cannot create symbolic link '/tmp/destination/symlink-1': No such file or directory
renamed 'symlink-2' -> '/tmp/destination/symlink-2'

Expected output:

'symlink-1' -> 'original'
'symlink-2' -> 'original'
mkdir: created directory '/tmp/destination'
'symlink-1' -> '/tmp/destination/symlink-1'
copied 'symlink-2' -> '/tmp/destination/symlink-2'
removed 'symlink-2'

If the target name is in an absolute format (IOW, it won't get broken after occurring in another dir), everything works across the FS just fine:

'symlink-1' -> '/D/bandom/original'
'symlink-2' -> '/D/bandom/original'
mkdir: created directory '/tmp/destination'
'symlink-1' -> '/tmp/destination/symlink-1'
copied 'symlink-2' -> '/tmp/destination/symlink-2'
removed 'symlink-2'

I tested that on fairly recent Cygwin too:

$ uname -a
CYGWIN_NT-10.0-19044 DESKTOP-O7JE7JE 3.4.10-1.x86_64 2023-11-29 12:12 UTC x86_64 Cygwin

It mostly works:

$ bash band.sh
'symlink-1' -> 'original'
'symlink-2' -> 'original'
mkdir: created directory '/tmp/destination'
'symlink-1' -> '/tmp/destination/symlink-1'
copied 'symlink-2' -> '/tmp/destination/symlink-2'
mv: listing attributes of 'symlink-2': Permission denied
removed 'symlink-2'

... with the following warning being added:

mv: listing attributes of '...': Permission denied

Please excuse me if this belongs to msys2/MSYS2-packages.