>From 827c17d1645cce8d37a4a65369bea29e36681f3e Mon Sep 17 00:00:00 2001
From: Daniel Mendler <mail@daniel-mendler.de>
Date: Mon, 19 Apr 2021 13:06:54 +0200
Subject: [PATCH 4/6] completion-all-sorted-completions: Respect completion
 boundaries

* lisp/minibuffer.el (completion-all-sorted-completions): When
building the hash of history positions drop the prefix as determined
by `completion-boundaries`. For file completions drop everything
behind the first "/".
---
 lisp/minibuffer.el | 36 +++++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index d728c791d3..c7aec9665e 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1396,14 +1396,36 @@ completion-all-sorted-completions
                 (let* ((hist (symbol-value minibuffer-history-variable))
                        (hash (make-hash-table :test #'equal :size (length hist)))
                        (index 0)
-                       (def (car-safe minibuffer-default)))
-                  ;; Record history positions in hash
-                  (dolist (c hist)
-                    (unless (gethash c hash)
-                      (puthash c index hash))
-                    (cl-incf index))
+                       (def (car-safe minibuffer-default))
+                       (bounds (completion-boundaries
+                                (substring string 0 (- (point) start))
+                                minibuffer-completion-table
+                                minibuffer-completion-predicate
+                                ""))
+                       (pre (substring string 0 (car bounds)))
+                       (pre-len (length pre)))
+                  ;; Default comes first.
                   (when (stringp def)
-                    (puthash def -1 hash))
+                    (setq hist (cons def hist)))
+                  ;; Record history positions in hash
+                  (if (equal "" pre)
+                      (progn
+                        (dolist (c hist)
+                          (unless (gethash c hash)
+                            (puthash c index hash))
+                          (cl-incf index)))
+                    ;; Remove prefix from history strings, in order to
+                    ;; handle completion boundaries.
+                    (dolist (c hist)
+                      (when (string-prefix-p pre c)
+                        ;; Special handling of file name candidates:
+                        ;; Drop everything after the first / after the prefix.
+                        (let ((pos (and minibuffer-completing-file-name
+                                        (string-match-p "/" c pre-len))))
+                          (setq c (substring c pre-len (and pos (1+ pos)))))
+                        (unless (gethash c hash)
+                          (puthash c index hash)))
+                      (cl-incf index)))
                   ;; Decorate elements with history position
                   (let ((c all))
                     (while c
-- 
2.20.1