From 1d42f4800bc3759ac961b97b2a66d4b73e520eb5 Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Fri, 9 Apr 2021 09:57:06 +0200
Subject: [PATCH] Fix hostname completion on MS Windows

* lisp/net/tramp.el (tramp-completion-file-name-regexp-default):
Handle volume letter being added to paths for file name completion on W32
systems.  This fixes hostname (and method) autocomplete on W32.

Copyright-paperwork-exempt: yes
---
 lisp/net/tramp.el | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index b2c650f6e1a..e61c3b1e44c 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -1078,7 +1078,13 @@ initial value is overwritten by the car of `tramp-file-name-structure'.")
 
 (defconst tramp-completion-file-name-regexp-default
   (concat
-   "\\`/\\("
+   "\\`"
+   ;; `file-name-completion' uses absolute paths for matching.  This
+   ;; means that on W32 systems, something like "/ssh:host:~/path"
+   ;; becomes "c:/ssh:host:~/path".  See also `tramp-drop-volume-letter'.
+   (when (eq system-type 'windows-nt)
+       "\\(?:[[:alpha:]]:\\)?")
+   "/\\("
    ;; Optional multi hop.
    "\\([^/|:]+:[^/|:]*|\\)*"
    ;; Last hop.
-- 
2.39.5