improve(segments,tab-bar): truncate long tab names

Adds new custom variable `whale-line-segments-tab-bar-width` and sets
it to 10 by default. Works the same as for projects.

To get the old behavior back this can be set to `nil`.

test/whale-line-segments-test.el

@@ -712,13 +712,18 @@
                      (whale-line-segments--project))))))
 
 (ert-deftest tab-bar ()
-  (let ((tab '((explicit-name . t) (name . "test-tab")))
-        (tab-bar-mode t))
+  (let ((tab '((explicit-name . t) (name . "test-tab-long-name")))
+        (tab-bar-mode t)
+        (whale-line-segments-tab-bar-width 10))
 
     (bydi ((:mock tab-bar--current-tab :return tab)
            (:risky-mock fboundp :with always))
 
-      (should (string= "test-tab" (whale-line-segments--tab-bar--identifier))))))
+      (should (string= (concat "test-tab-" (truncate-string-ellipsis)) (whale-line-segments--tab-bar--identifier)))
+
+      (setq whale-line-segments-tab-bar-width nil)
+
+      (should (string= "test-tab-long-name" (whale-line-segments--tab-bar--identifier))))))
 
 ;;;; VC
 

whale-line-segments.el

@@ -96,6 +96,14 @@ If this is a number, a name exceeding it will be truncated."
   :type '(choice (integer :tag "The (padded) width")
                  (const :tag "Full name" nil)))
 
+(defcustom whale-line-segments-tab-bar-width 10
+  "The width of the tab-bar name.
+
+If this is a number, a name exceeding it will be truncated."
+  :group 'whale-line-segments
+  :type '(choice (integer :tag "The (padded) width")
+                 (const :tag "Full name" nil)))
+
 ;;;; Utility
 
 (defun whale-line-segments--decorate (_symbol &rest _args)
@@ -879,7 +887,11 @@ Only consider Dired buffers and file buffers."
   (when-let* ((tab (tab-bar--current-tab))
               (name (alist-get 'name tab)))
 
-    name))
+    (if (numberp whale-line-segments-tab-bar-width)
+        (truncate-string-to-width
+         name whale-line-segments-tab-bar-width nil nil
+         (truncate-string-ellipsis))
+      name)))
 
 (defvar whale-line-segments--tab-bar
   '((tab-bar-mode