There are several Subversion workflows and properties that are similar to existing functionality on GitHub.

Executable files (svn:executable)

We convert svn:executable properties by updating the file mode directly before adding it to the Git repository.

MIME types (svn:mime-type)

GitHub internally tracks the mime-type properties of files and the commits that added them.

Ignoring unversioned items (svn:ignore)

If you've set files and directories to be ignored in Subversion, GitHub will track them internally. Files ignored by subversion clients are completely distinct from entries in a .gitignore file.

Currently unsupported properties

GitHub doesn't currently support svn:externals, svn:global-ignores, or any properties not listed above, including custom properties.