There is nothing wrong here. HM is just reminding you that you are working on a file in a compressed format (like .hmxz, the .hmskin format is really a ZIP archive) that cannot be properly managed by version control. If you want your version edits on the components of the skin to be managed by version control you need to work on an unpacked version of the skin, which is quite possible. However, you need to unpack it manually, as follows:
- Create an empty folder in your SVN managed area for your unpacked skin.
- Change the extension of the skin from .hmskin to .zip and unpack its contents into the new folder.
- Change the name of the project.hmxp file to your_skin_name.hmskin
- Use your SVN client tools (probably Tortoise) to add all the contents of the folder to your version control repository
You can edit the unpacked skin directly with Help+Manual or Premium Pack Toolbox, and you can also select it for publishing in the Publish screen in Help+Manual. The only restriction is that the preview image stored in the skin will not be displayed in the Publish screen. Repacking the finished skin:
- Change the name of the unpacked .hmskin file back to project.hmxp.
- Pack all the contents of the folder in a new .zip file.
- Change the extension of the .zip file to .hmskin