peek_path

Exactly like get_path, but caches the result via set_qdata_full.

This is useful for example in C applications which mix `g_file_*` APIs with native ones. It also avoids an extra duplicated string when possible, so will be generally more efficient.

This call does no blocking I/O.

Parameters:

this	input File

Returns:

string containing the File's path, or null if no such path exists. The returned string is owned by this.