Support of cygwin symlinks in docker

[pyhedgehog]

cygwin-shell#L30 "docker image does not support cygwin symlink"

If reason for this problem is that by default cygwin creates symlink as NTFS symlink then adding CYGWIN=winsymlinks:lnk can help.

Hi @pyhedgehog, thank you very much.

I remember I tested CYGWIN=winsymlinks:lnk but it doesn't work either, because cygwin requires file attributes FILE_ATTRIBUTE_READONLY/FILE_ATTRIBUTE_READONLY to distinguish normal file and Cygwin fake lnk file, however, on Linux, there is no known way to emulate those attributes on AUFS filesystem yet. Also see https://bugs.wine-staging.com/show_bug.cgi?id=403 for related issue.

I might be wrong and will double check later, let's keep the issue open, thank you.

If we could convince Cygwin accept the deep copy patch from Msys2, then it will be a solution:
https://github.com/Alexpux/MSYS2-packages/blob/master/msys2-runtime/0006-Do-not-create-cygwin-symlinks.-Instead-use-deep-copy.patch

[pyhedgehog]

Shouldn't it be better to use any .lnk file as symlink on unsupported filesystems? I.e. CYGWIN=winsymlinks:lnkany.

@pyhedgehog I couldn't find lnkany in Cygwin source code, could you confirm or maybe provide a reference document?

[pyhedgehog]

It's proposal. Sorry for misguiding.