>From a09ea8f4eb9a341f6c4ab090ec0c49acf070589a Mon Sep 17 00:00:00 2001
From: Daniel Mendler <mail@daniel-mendler.de>
Date: Tue, 20 Apr 2021 00:01:44 +0200
Subject: [PATCH] completion-all-sorted-completions: Add completion boundary
 support

Remove the completion prefix from the history elements.  This is a
heuristic which does not work for all completion styles.  In
particular when using partial-completion or initials, the candidates
contain directories. Is there a better more general solution?

minibuffer.el (completion-all-sorted-completions): The history is
preprocessed by the function `minibuffer--sort-preprocess-history`.
---
 lisp/minibuffer.el | 49 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 40 insertions(+), 9 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 4ed596430c..d340aec98b 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1381,6 +1381,42 @@ minibuffer--sort-by-length-alpha
                     (and (= (length c1) (length c2))
                          (string< c1 c2))))))
 
+(defun minibuffer--sort-preprocess-history (start string)
+  "Preprocess history, remove completion prefixes.
+STRING is the minibuffer content.
+START is the start position of the completion."
+  (let* ((def (car-safe minibuffer-default))
+         (hist (symbol-value minibuffer-history-variable))
+         (hist (if def (cons def hist) hist))
+         (bounds (completion-boundaries
+                  (substring string 0 (- (point) start))
+                  minibuffer-completion-table
+                  minibuffer-completion-predicate
+                  ""))
+         (pre (substring string 0 (car bounds)))
+         (pre-len (length pre)))
+    ;; Preprocess history if completion boundaries are used
+    (cond
+     ;; Special handling of file name candidates.
+     ;; Drop prefix and everything after the first "/".
+     (minibuffer-completing-file-name
+      (setq hist (delq nil
+                       (mapcar
+                        (lambda (c)
+                          (when (string-prefix-p pre c)
+                            (let ((pos (string-match-p "/" c pre-len)))
+                              (substring c pre-len (and pos (1+ pos))))))
+                        hist))))
+     ;; Drop prefix before the completion boundary
+     ((/= pre-len 0)
+      (setq hist
+            (delq nil (mapcar
+                       (lambda (c)
+                         (when (string-prefix-p pre c)
+                           (substring c pre-len)))
+                       hist))))
+     (t hist))))
+
 (defun completion-all-sorted-completions (&optional start end)
   (or completion-all-sorted-completions
       (let* ((start (or start (minibuffer-prompt-end)))
@@ -1410,21 +1446,16 @@ completion-all-sorted-completions
           (setq all (delete-dups all))
           (setq last (last all))
 
-          (cond
-           (sort-fun
-            (setq all (funcall sort-fun all)))
-           (t
+          (if sort-fun
+              (setq all (funcall sort-fun all))
             ;; Sort first by length and alphabetically.
             (setq all (minibuffer--sort-by-length-alpha all))
-
             ;; Sort by history position, put the default, if it
             ;; exists, on top.
             (when (and (minibufferp) (not (eq minibuffer-history-variable t)))
-              (let ((def (car-safe minibuffer-default))
-                    (hist (symbol-value minibuffer-history-variable)))
               (setq all (minibuffer--sort-by-position
-                         (if def (cons def hist) hist)
-                         all))))))
+                         (minibuffer--sort-preprocess-history start string)
+                         all))))
 
           ;; Cache the result.  This is not just for speed, but also so that
           ;; repeated calls to minibuffer-force-complete can cycle through
-- 
2.20.1