Show Line Length Indicator at 72 Characters for Commit Messages

This is recommended line length for commit messages.

Screenshot: https://imgur.com/a/Mi8dOLR

Google-Bug-Id: b/361035569
Release-Notes: skip
Change-Id: Iadaac002ad7be33f69bac2fe5e051ff501e964bf

web/element/codemirror-element.ts

diff --git a/web/element/codemirror-element.ts b/web/element/codemirror-element.ts
index 98dd811..206d7fd 100644
--- a/web/element/codemirror-element.ts
+++ b/web/element/codemirror-element.ts
@@ -113,13 +113,17 @@
             this.darkMode
           ),
           EditorView.updateListener.of(update => {
-            if (this.prefs?.line_length) {
+            // Set ruler width to 72 for commit messages,
+            // as this is the recommended line length for git commit messages.
+            if (this.fileType?.includes('x-gerrit-commit-message')) {
+              updateRulerWidth(72, update.view.defaultCharacterWidth, true);
+            } else if (this.prefs?.line_length) {
               // This is required to be in the setTimeout() to ensure the
               // line is set as correctly as possible.
               updateRulerWidth(
-                  this.prefs.line_length,
-                  update.view.defaultCharacterWidth,
-                  true
+                this.prefs.line_length,
+                update.view.defaultCharacterWidth,
+                true
               );
             }