syscall: windows doesn't allow renames for read-only files

[zx2c4]

On Windows, right now we map the lack of the writable bit in Unix file permissions to FILE_ATTRIBUTES_READONLY. This sort of works fine, but this actually prohibits rename-in-place, whereas it's allowed on Unix.

I'm not suggesting that we change this mapping to something else right now, but in case things pop up down the line related to this, here's a bug to track it.

cc @bcmills @alexbrainman

[bcmills]

CC @jayconrod

Is there anything to actively do for this issue? (Should we leave it open, or close it and just use it as a point of reference?)

[networkimprov]

At least we should document the behavior.

[slrz]

The file system behaviour itself is already documented as part of the OS. As long as Go doesn't do anything special to prevent the rename, that's exactly where that documentation should live.

It might make sense to document the mapping of Unix permission bits to Windows file attributes though.

[bcmills]

@slrz, the Go os and syscall packages map to Windows system calls in a non-trivial way, particularly where file permissions are concerned. The documentation supplied “as part of the OS” does not describe that mapping.