cd path arg can be a symbol (shell ease)

Signed-off-by: Ava Affine <ava@sunnypup.io>

Readme.org

@@ -166,7 +166,6 @@ Note: this section only tracks the state of incomplete TODO items. Having everyt
 - Can pass args to flesh scripts (via command line)
 - Can pass args to flesh scripts (via interpreter)
 - tab completion for symbols also attempts to complete binaries
-- cd accepts symbols as well as strings (emulate shell)
 - declare macros
 - Release CI
 - Make an icon if you feel like it

Shell.org

@@ -146,6 +146,10 @@ Flesh also provides a ~cd~ utility to change current working directory:
 This ~cd~ routine will keep the ~PWD~ variable up to date.
 Every invokation of ~cd~ will call whatever lambda or function is stored in ~CFG_FLESH_CD_CB~ with no arguments. A function stored in this variable can then perform on the fly reconfiguration or set additional variables based on the directory that the user has entered.
 
+WARNING: Symbols will be taken as strings unless wrapped in a form.
+  > Example: cd HOME => cd 'HOME'
+  > Example: cd (eval HOME) => cd /path/to/home/dir
+
 ** Creating bindings for shell commands
 Daily Flesh users will long for first class shell commands that are accounted for in autocomplete.
 

src/stl/posix.rs

@@ -715,9 +715,12 @@ fn fg_callback(
 }
 
 const CD_DOCSTRING: &str =
-    "Expects 1 argument (a string). Changes to a new directory.
+    "Expects 1 argument (a string, symbol, or form). Changes to a directory.
+WARNING: Symbols will be taken as strings unless wrapped in a form.
+  > Example: cd HOME => cd 'HOME'
+  > Example: cd (eval HOME) => cd /path/to/home/dir
 If CFG_RELISH_CD_CB is defined, cd will evaluate it.
-cd returns the result that CFG_RELISH_CD_CB returns.";
+cd returns the result that CFG_RELISH_CD_CB returns, or None";
 fn cd_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let dir: &String;
     match *ast.car {