Possible issue with usage of `File.getCanonicalPath()`

[iadcode]

Pull Request #47 changed the sources list to be transformed through File.getCanonicalPath().
Additionally, in SbtJsTask.executeSourceFilesJs, a file is transformed by File.getCanonicalPath().

I question the use of .getCanonicalPath() over .getAbsolutePath(). On UNIX environments, .getCanonicalPath() will resolve symbolic links. With the inconsistent usage of .getCanonicalPath() throughout SbtJsTask, I think this causes issues when mapping output files to source files, or trying to locate source/output files relative to some folders.

I have created an example using Play to demonstrate this in practice at objectmastery/canonical-error-example. The example uses a project/subproject setup, with a symbolic link from the main project to the sub project. This reflects a setup I already have working fine on Windows, with a subproject being symbolically linked to by multiple other main projects (code sharing! yay!).

Of course, there's always a chance .getCanonicalPath() is all fine and I'm just doing something strange, so feel free to point that out instead.

[iadcode]

The solution may also be to consistently use .getCanonicalPath() everywhere instead, so you're never dealing with a path with a symbolic link.

[jroper]

I think it should probably use getAbsolutePath, sbt's relativeTo will fail if there are symlinks underneath a the parent directory to somewhere outside of the structure.