~0 is the top of the directory stack, always the same as $PWD.
If the characters following the tilde in the tilde-prefix consist of
a number N, optionally prefixed by a '+' or a '-', the tilde-prefix is
replaced with the corresponding element from the directory stack, as it
would be displayed by the 'dirs' builtin invoked with the characters
following tilde in the tilde-prefix as an argument (*note The Directory
Stack::). If the tilde-prefix, sans the tilde, consists of a number
without a leading '+' or '-', '+' is assumed.
--
Andreas Schwab, [email protected]
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."