Optimize vc-hg-state for directories

Directories are never tracked in hg, so it's pointless to run
vc-hg-state on them.  And, in fact, our implementation previously
would list all the files contained in the directory and then parse
that in Emacs, which is very slow in large repos.

Let's just use the knowledge that directories aren't tracked in hg,
and skip running hg entirely.

* lisp/vc/vc-hg.el (vc-hg-state): Return nil for
directories.  (Bug#66364)

diff --git a/lisp/vc/vc-hg.el b/lisp/vc/vc-hg.el
index c3e563a1f10bdc6fb4ff2f66923691ef6b7898fb..f2ee9ef35e404b0cbb2219fd2aed58fdecdfbae1 100644 (file)
--- a/lisp/vc/vc-hg.el
+++ b/lisp/vc/vc-hg.el
@@ -216,8 +216,9 @@ If `ask', you will be prompted for a branch type."
 
 (defun vc-hg-state (file)
   "Hg-specific version of `vc-state'."
-  (let ((state (vc-hg-state-fast file)))
-    (if (eq state 'unsupported) (vc-hg-state-slow file) state)))
+  (unless (file-directory-p file)
+    (let ((state (vc-hg-state-fast file)))
+      (if (eq state 'unsupported) (vc-hg-state-slow file) state))))
 
 (defun vc-hg-state-slow (file)
   "Determine status of FILE by running hg."