ox: Fix extra character deletion after link

* lisp/ox.el (org-export--update-included-link): Account
for :post-blank property when inserting back the link.
* testing/lisp/test-ox.el (test-org-export/expand-include/links): Add
test.

Fixes bug#39173.

lisp/ox.el

@@ -3461,15 +3461,16 @@ Move point after the link."
 	(goto-char (org-element-property :end link))
       (let ((new-path (file-relative-name (expand-file-name path file-dir)
 					  includer-dir))
-	    (new-link (org-element-copy link))
-	    (contents (and (org-element-property :contents-begin link)
-			   (buffer-substring
-			    (org-element-property :contents-begin link)
-			    (org-element-property :contents-end link)))))
+	    (new-link (org-element-copy link)))
 	(org-element-put-property new-link :path new-path)
+	(when (org-element-property :contents-begin link)
+	  (org-element-adopt-elements new-link
+	    (buffer-substring
+	     (org-element-property :contents-begin link)
+	     (org-element-property :contents-end link))))
 	(delete-region (org-element-property :begin link)
 		       (org-element-property :end link))
-	(insert (org-element-link-interpreter new-link contents))))))
+	(insert (org-element-interpret-data new-link))))))
 
 (defun org-export--prepare-file-contents
     (file &optional lines ind minlevel id footnotes includer)

testing/lisp/test-ox.el

@@ -1440,6 +1440,28 @@ Footnotes[fn:2], foot[fn:test] and [fn:inline:inline footnote]
 	    (kill-buffer buffer))
 	  (when (file-exists-p subdir) (delete-directory subdir t))
 	  (when (file-exists-p includer) (delete-file includer)))))))
+  ;; Preserve relative bracket links without description.
+  (should
+   (string-suffix-p
+    "foo.org]] :tag:"
+    (let* ((subdir (make-temp-file "org-includee-" t))
+	   (includee (expand-file-name "includee.org" subdir))
+	   (includer (make-temp-file "org-includer-")))
+      (write-region "[[file:foo.org]] :tag:" nil includee)
+      (write-region (format "#+INCLUDE: %S"
+			    (file-relative-name includee
+						temporary-file-directory))
+		    nil includer)
+      (let ((buffer (find-file-noselect includer t)))
+	(unwind-protect
+	    (with-current-buffer buffer
+	      (org-export-expand-include-keyword)
+	      (org-trim (buffer-string)))
+	  (when (buffer-live-p buffer)
+	    (with-current-buffer buffer (set-buffer-modified-p nil))
+	    (kill-buffer buffer))
+	  (when (file-exists-p subdir) (delete-directory subdir t))
+	  (when (file-exists-p includer) (delete-file includer)))))))
   ;; Preserve relative bracket links with description.
   (should
    (string-prefix-p