configurable cd hook

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

Readme.org

@@ -68,6 +68,7 @@ Errors during configuration are non-terminal. In such a case any defaults which
 - CFG_FLESH_L_PROMPT (default 'λ'): a function that is called with no arguments to output the left hand of the prompt
 - CFG_FLESH_R_PROMPT (default ''): a function that is called with no arguments to output the right hand of the prompt
 - CFG_FLESH_PROMPT_DELIMITER (default '>'): a function that is called with no arguments to output the delimiter separating prompt from user input
+- CFG_FLESH_CD_CB (default None): optional function / lambda that is called with no arguments on every change of CD. See [[file:Shell.org][The Shell Documentation]] for more information.
 
 ** Prompt design
 For an example of prompt design see [[file:snippets/mood-prompt.f][the mood prompt]]
@@ -164,18 +165,17 @@ Note: this section only tracks the state of incomplete TODO items. Having everyt
 ** TODO v1.0 tasks
 - Can pass args to flesh scripts (via command line)
 - Can pass args to flesh scripts (via interpreter)
-- Pipe also operates on stderr
-- ~ if possible (string replacement?)
 - tab completion for symbols also attempts to complete binaries
-- finish basic goals in the [[file:snippets/interactive-devel.f][interactive development library]]
+- cd accepts symbols as well as strings (emulate shell)
+- declare macros
 - Release CI
 - Make an icon if you feel like it
 - Post release to relevant channels
 ** TODO v1.1 tasks
-- emacs lsp implementation
-- finish stretch goals in the [[file:snippets/interactive-devel.f][interactive development library]]
+- Pipe also operates on stderr
+- better emacs language mode
+- finish the [[file:snippets/interactive-devel.f][interactive development library]]
 - History length configurable (env var?)
-- execute configurable function on cd
 - Post to relevant channels
 - Implement Compose for lambdas
   (add to readme)