Absolute path from user input without losing symlinks inside

Is it possible to convert in a shell script a user input path (absolute or relative) to the absolute path but without losing the symlinks inside, e.g. /a/b/c is the current user dir and c is a symlink to /a/b/s:

input .      => result /a/b/c
input ./d    => result /a/b/c/d
input ../c   => result /a/b/c
input /a/b/c => result /a/b/c
(readlink converts it to /a/b/s, but I need /a/b/c)