Updating does not work if mod folder contains a file/folder starting with a dot

[jan-di]

Steps to reproduce:

1. Take a mod which has an update identifier and install it normally.
2. Change something and update to revert changes. -> should work.
3. Create a file starting with a dot in the mod folder, e.g. ".gitignore"
4. Try to update the mod to revert changes -> BLT says the update is done, but the log shows an error:

PM Lua: [Downloads] Verifying...
PM Lua: [Downloads] Removing old installation...
PM Log:  (..\src\util\util.cpp:100) MoveFileEx failed with error 183
PM Lua: [Downloads] Complete!

and in the mod folder, all files and folders except the one starting with a dot are deleted.