tramp: Localname deconstruction
8.1 Splitting a localname into its component parts
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TRAMP package redefines lisp functions ‘file-name-directory’ and
‘file-name-nondirectory’ to accommodate the unique file naming syntax
that TRAMP requires.
The replacements dissect the file name, use the original handler for
the localname, take that result, and then re-build the TRAMP file name.
By relying on the original handlers for localnames, TRAMP benefits from
platform specific hacks to the original handlers.