feat(navigation): Improve narrowing with recursive-narrow package

Additionally allow `recursive-narrow-or-widen-dwin` to also trigger
`org-edit-src-code` within org buffers. This technically does not use
narrowing, but it does "focus" on the source code block for editing, so
it at least in spirit embodies the intent of narrowing.

This behavior was inspired by:
https://endlessparentheses.com/emacs-narrow-or-widen-dwim.html

core/siren-core-modules.el

@@ -62,6 +62,7 @@
 (require 'siren-helm-ag)
 (require 'siren-helm-open-github)
 (require 'siren-helm-swoop)
+(require 'siren-recursive-narrow)
 (require 'siren-scroll-half-screen)
 
 ;; Project management

modules/navigation/siren-recursive-narrow.el

@@ -0,0 +1,24 @@
+;;; siren-recursive-narrow.el --- jimeh's Emacs Siren: recursive-narrow configuration.
+
+;;; Commentary:
+
+;; Basic configuration for recursive-narrow.
+
+;;; Code:
+
+(use-package recursive-narrow
+  :bind
+  ("C-x C-n" . recursive-narrow-or-widen-dwim)
+  ("C-x n w" . recursive-widen)
+  ("C-x n n" . recursive-narrow-or-widen-dwim)
+
+  :config
+  (add-hook 'recursive-narrow-dwim-functions
+            'siren-recursive-narrow-org-edit-src-code)
+
+  :init
+  (defun siren-recursive-narrow-org-edit-src-code()
+    (ignore-errors (org-edit-src-code) t)))
+
+(provide 'siren-recursive-narrow)
+;;; siren-recursive-narrow.el ends here

modules/org-mode/siren-org-mode.el

@@ -13,16 +13,21 @@
 (require 'siren-smartparens)
 
 (use-package org
-  :bind (:map org-mode-map
-              ("C-j" . org-return-indent)
-              ("RET" . org-return-indent)
-              ("M-{" . org-promote-subtree)
-              ("M-}" . org-demote-subtree)
-              ("M-P" . org-metaup)
-              ("M-N" . org-metadown)
-              ("C-M-n" . outline-next-visible-heading)
-              ("C-M-p" . outline-previous-visible-heading))
-  :hook (org-mode . siren-org-mode-setup)
+  :bind
+  (:map org-mode-map
+        ("C-j" . org-return-indent)
+        ("RET" . org-return-indent)
+        ("M-{" . org-promote-subtree)
+        ("M-}" . org-demote-subtree)
+        ("M-P" . org-metaup)
+        ("M-N" . org-metadown)
+        ("C-M-n" . outline-next-visible-heading)
+        ("C-M-p" . outline-previous-visible-heading))
+  (:map org-src-mode-map
+        ("C-c C-c" . org-edit-src-exit))
+
+  :hook
+  (org-mode . siren-org-mode-setup)
 
   :custom
   (org-blank-before-new-entry '((heading . auto) (plain-list-item . nil)))