Add initial treemacs module

modules/ui/treemacs/config.el

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+;;; ui/treemacs/config.el -*- lexical-binding: t; -*-
+
+(defvar treemacs-use-git-mode
+  (pcase (cons (not (null (executable-find "git")))
+               (not (null (executable-find "python3"))))
+    (`(t . t) 'extended)
+    (`(t . _) 'simple))
+  "Type of git integration for `treemacs-git-mode'.
+There are 2 possible values:
+1) simple, which highlights only files based on their git status, and is
+   slightly faster
+2) extended, which highlights both files and directories, but requires python")
+
+(def-package! treemacs
+  :commands (treemacs treemacs-find-file treemacs-bookmark)
+  :config
+  (setq treemacs-no-png-images t
+        treemacs-follow-after-init t
+        treemacs-width 35
+        treemacs-position 'left
+        treemacs-is-never-other-window t
+        treemacs-silent-refresh nil
+        treemacs-indentation 2
+        treemacs-sorting 'alphabetic-desc
+        treemacs-show-hidden-files t
+        treemacs-goto-tag-strategy 'refetch-index
+        treemacs-collapse-dirs (if (executable-find "python3") 3 0))
+  (treemacs-follow-mode t)
+  (treemacs-filewatch-mode t)
+  (when (memq treemacs-use-git-mode '(simple extended))
+    (treemacs-git-mode treemacs-use-git-mode)))
+
+(add-hook! 'doom-post-init-hook
+  (map! :leader
+        :prefix "f"
+        :desc "Open treemacs" :nv "t" #'treemacs
+        :desc "Find file in treemacs" :nv "T" #'treemacs-find-file
+        :desc "Go to bookmark" :nv "b" #'treemacs-bookmark))
+
+(def-package! treemacs-evil
+  :after (treemacs evil)
+  :if (featurep! :feature evil))
+
+(def-package! treemacs-projectile
+  :after (treemacs projectile))

modules/ui/treemacs/packages.el

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+;; -*- no-byte-compile: t; -*-
+;;; ui/treemacs/packages.el
+
+(package! treemacs)
+(when (featurep! :feature evil)
+  (package! treemacs-evil))
+(package! treemacs-projectile)