Lighttpd

webdav properties are preserved on a PUT of an existing file.

The reason for replacing the existing file is that the PUT request might fail to upload somewhere in the middle, and so the upload is done to a temporary file before copying into place. It should generally be discouraged to write into an existing file (same inode) that others might be in the middle of reading.

Question: Are you suggesting that lighttpd mod_webdav should attempt to preserve the permission mode when a PUT is made on an existing file? That might be useful when accessing a directory tree via webdav and via alternative means, but it is easy to corrupt webdav properties if someone is moving files around the webdav tree via alternative means (without using webdav), e.g. by direct modification via mv and cp.

See alternative in https://redmine.lighttpd.net/boards/2/topics/11311