improve(segments,project): customizable width before truncation

Adds new custom variable `whale-line-segments-project-width` that
defaults to 10. If the name of the project exceeds this numer, it is
truncated using `truncate-string-to-width`.

The old behavior can be restored by setting this to `nil`.

test/whale-line-segments-test.el

@@ -685,7 +685,8 @@
       (should (string= "Project (/home/test/project/)\nmouse-1: Open root" (whale-line-segments--project--help)))))
 
 (ert-deftest project--get--for-project ()
-  (let ((whale-line-segments--project--map nil))
+  (let ((whale-line-segments--project--map nil)
+        (whale-line-segments-project-width nil))
 
     (bydi ((:always whale-line-segments--project--display-for-buffer-p)
            (:always project-current)
@@ -699,6 +700,15 @@
                                             mouse-face whale-line-highlight
                                             help-echo "help"
                                             local-map nil))
+                     (whale-line-segments--project)))
+
+      (setq whale-line-segments-project-width 3)
+
+      (should (equal `("*" " " (:propertize ,(concat "pr" (truncate-string-ellipsis))
+                                            face whale-line-emphasis
+                                            mouse-face whale-line-highlight
+                                            help-echo "help"
+                                            local-map nil))
                      (whale-line-segments--project))))))
 
 (ert-deftest tab-bar ()

whale-line-segments.el

@@ -88,6 +88,14 @@ In project buffers segments are calculated relative to the project root."
   :group 'whale-line-segments
   :type 'string)
 
+(defcustom whale-line-segments-project-width 10
+  "The width of the project 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)
@@ -845,11 +853,15 @@ Only consider Dired buffers and file buffers."
   (when-let* ((candidate (whale-line-segments--project--display-for-buffer-p))
               (project (project-current))
               (name (project-name project))
+              (truncated (if (and (numberp whale-line-segments-project-width)
+                                  (> (length name) whale-line-segments-project-width))
+                             (truncate-string-to-width name whale-line-segments-project-width 0 nil t)
+                           name))
               (help (whale-line-segments--project--help)))
 
     `(,@(when-let ((decorated (whale-line-segments--decorate 'project)))
           (list decorated (whale-line--spacer)))
-      (:propertize ,name
+      (:propertize ,truncated
                    face whale-line-emphasis
                    mouse-face whale-line-highlight
                    help-echo ,help