fix(modeline): key VC cache on resolved truename for symlink moves

The VC modeline cache keyed on (list file cj/modeline-vc-show-remote). If file was a symlink whose target moved to a different VC tree (shared drives, CI workspaces), the key was unchanged and the cache kept serving the old branch/state.

Added the resolved file-truename to the key, so a symlink re-pointed at a new target produces a different key and the cache refreshes. The extra file-truename is one stat per modeline refresh, cheap next to the VC calls the cache exists to avoid. Tests cover truename inclusion, key stability for an unchanged file, and a symlink whose target moves.

1 files changed, 6 insertions, 2 deletions

diff --git a/modules/modeline-config.el b/modules/modeline-config.el
index 61ab0f9d..5afe226e 100644
--- a/modules/modeline-config.el
+++ b/modules/modeline-config.el
@@ -129,8 +129,12 @@ Uses built-in cached values for performance.")
         cj/modeline-vc-cache-set-p nil))
 
 (defun cj/modeline-vc-cache-key (file)
-  "Return the cache key for FILE."
-  (list file cj/modeline-vc-show-remote))
+  "Return the cache key for FILE.
+Includes the resolved `file-truename' so that if FILE is a symlink whose
+target moves to a different VC tree, the key changes and the cache is not
+served a stale backend.  The extra `file-truename' is one stat per refresh,
+cheap next to the VC calls the cache avoids."
+  (list file (file-truename file) cj/modeline-vc-show-remote))
 
 (defun cj/modeline-vc-cache-valid-p (key now)
   "Return non-nil when cached VC data is valid for KEY at NOW."