regexp used to detect a script's interpretor.
adds a global entry in the `file-name-handler-alist'. (eshell-script-interpreter): Allow whitespace after the #! of a shell interpretor specification.
determines the initial character that forces use of an external version of a command. The default is *, but may be set to \, for example. (eshell-explicit-command): Use `eshell-explicit-command-char' instead of ?*.
functions (which all deal with filesystem entities, and never Lisp numerical values): eshell/cd, eshell/pushd, eshell/popd, eshell/ls, eshell/source, eshell/., eshell/man, eshell/rm, eshell/mkdir, eshell/rmdir, eshell/mv, eshell/cp, eshell/ln, eshell/cat, eshell/make, eshell/diff, eshell/locate, eshell/occur, eshell/which, eshell/addpath.
