Account for duplicated commands with different transient behavior

Previously "b" could be used to invoke `transient-echo-arguments'
in this example:

  (transient-define-prefix demo ()
    [("a" transient-echo-arguments :inapt-if ignore)
     ("b" transient-echo-arguments :inapt-if always)
     ("c" transient-echo-arguments :inapt-if ignore)])

lisp/transient.el

@@ -2046,36 +2046,40 @@ of the corresponding object."
       (define-key map [handle-switch-frame] #'transient--do-suspend))
     (dolist (obj transient--suffixes)
       (let* ((cmd (oref obj command))
+             (id (vector cmd))
              (kind (cond ((get cmd 'transient--prefix)    'prefix)
                          ((cl-typep obj 'transient-infix) 'infix)
-                         (t                               'suffix))))
-        (cond
-         ((oref obj inapt)
-          (define-key map (vector cmd) #'transient--do-warn-inapt))
-         ((slot-boundp obj 'transient)
-          (define-key map (vector cmd)
-            (pcase (list kind
-                         (transient--resolve-pre-command (oref obj transient))
-                         return)
-              (`(prefix   t ,_) #'transient--do-recurse)
-              (`(prefix nil ,_) #'transient--do-stack)
-              (`(infix    t ,_) #'transient--do-stay)
-              (`(suffix   t ,_) #'transient--do-call)
-              ('(suffix nil  t) #'transient--do-return)
-              (`(,_     nil ,_) #'transient--do-exit)
-              (`(,_     ,do ,_) do))))
-         ((not (lookup-key transient-predicate-map (vector cmd)))
-          (define-key map (vector cmd)
-            (pcase (list kind default return)
-              (`(prefix ,(or 'transient--do-stay 'transient--do-call) ,_)
-               #'transient--do-recurse)
-              (`(prefix   t ,_) #'transient--do-recurse)
-              (`(prefix  ,_ ,_) #'transient--do-stack)
-              (`(infix   ,_ ,_) #'transient--do-stay)
-              (`(suffix   t ,_) #'transient--do-call)
-              ('(suffix nil  t) #'transient--do-return)
-              (`(suffix nil ,_) #'transient--do-exit)
-              (`(suffix ,do ,_) do)))))))
+                         (t                               'suffix)))
+             (pre (cond
+                   ((oref obj inapt) #'transient--do-warn-inapt)
+                   ((slot-boundp obj 'transient)
+                    (pcase (list kind
+                                 (transient--resolve-pre-command
+                                  (oref obj transient))
+                                 return)
+                      (`(prefix   t ,_) #'transient--do-recurse)
+                      (`(prefix nil ,_) #'transient--do-stack)
+                      (`(infix    t ,_) #'transient--do-stay)
+                      (`(suffix   t ,_) #'transient--do-call)
+                      ('(suffix nil  t) #'transient--do-return)
+                      (`(,_     nil ,_) #'transient--do-exit)
+                      (`(,_     ,do ,_) do)))
+                   ((not (lookup-key transient-predicate-map id))
+                    (pcase (list kind default return)
+                      (`(prefix ,(or 'transient--do-stay 'transient--do-call) ,_)
+                       #'transient--do-recurse)
+                      (`(prefix   t ,_) #'transient--do-recurse)
+                      (`(prefix  ,_ ,_) #'transient--do-stack)
+                      (`(infix   ,_ ,_) #'transient--do-stay)
+                      (`(suffix   t ,_) #'transient--do-call)
+                      ('(suffix nil  t) #'transient--do-return)
+                      (`(suffix nil ,_) #'transient--do-exit)
+                      (`(suffix ,do ,_) do))))))
+        (when pre
+          (if-let ((alt (lookup-key map id)))
+              (unless (eq alt pre)
+                (define-key map (vconcat (oref obj key) id) pre))
+            (define-key map id pre)))))
     map))
 
 (defun transient--make-redisplay-map ()
@@ -2812,7 +2816,8 @@ exit."
 ;;; Pre-Commands
 
 (defun transient--call-pre-command ()
-  (if-let ((fn (transient--get-pre-command this-command)))
+  (if-let ((fn (transient--get-pre-command this-command nil
+                                           (this-command-keys-vector))))
       (let ((action (funcall fn)))
         (when (eq action transient--exit)
           (setq transient--exitp (or transient--exitp t)))
@@ -2824,10 +2829,14 @@ exit."
         (setq this-command 'transient-undefined)))
     transient--stay))
 
-(defun transient--get-pre-command (&optional cmd enforce-type)
+(defun transient--get-pre-command (&optional cmd enforce-type keys)
   (or (and (not (eq enforce-type 'non-suffix))
            (symbolp cmd)
-           (lookup-key transient--predicate-map (vector cmd)))
+           (or (and keys
+                    (let ((def (lookup-key transient--predicate-map
+                                           (vconcat keys (list cmd)))))
+                      (and (symbolp def) def)))
+               (lookup-key transient--predicate-map (vector cmd))))
       (and (not (eq enforce-type 'suffix))
            (transient--resolve-pre-command
             (oref transient--prefix transient-non-suffix)