ox.el: Infer :minlevel for INCLUDE-keywords

* ox.el (org-export-expand-include-keyword): Infer :minlevel for
included Org documents if not set explicitly.
* test-ox.el (org-export-expand-include-keyword): Add tests for inferred :minlevel.

lisp/ox.el

@@ -3063,10 +3063,20 @@ storing and resolving footnotes.  It is created automatically."
   (let ((case-fold-search t)
 	(file-prefix (make-hash-table :test #'equal))
 	(current-prefix 0)
-	(footnotes (or footnotes (make-hash-table :test #'equal))))
+	(footnotes (or footnotes (make-hash-table :test #'equal)))
+	(include-re "^[ \t]*#\\+INCLUDE:"))
+    ;; If :minlevel is not set the text-property
+    ;; `:org-include-induced-level' will be used to determine the
+    ;; relative level when expanding INCLUDE.
+    ;; Only affects included Org documents.
     (goto-char (point-min))
+    (while (re-search-forward include-re nil t)
+      (put-text-property (line-beginning-position) (line-end-position)
+			 :org-include-induced-level
+			 (1+ (org-reduced-level (or (org-current-level) 0)))))
     ;; Expand INCLUDE keywords.
-    (while (re-search-forward "^[ \t]*#\\+INCLUDE:" nil t)
+    (goto-char (point-min))
+    (while (re-search-forward include-re nil t)
       (let ((element (save-match-data (org-element-at-point))))
 	(when (eq (org-element-type element) 'keyword)
 	  (beginning-of-line)
@@ -3111,8 +3121,7 @@ storing and resolving footnotes.  It is created automatically."
 		       (if (string-match ":minlevel +\\([0-9]+\\)" value)
 			   (prog1 (string-to-number (match-string 1 value))
 			     (setq value (replace-match "" nil nil value)))
-			 (let ((cur (org-current-level)))
-			   (if cur (1+ (org-reduced-level cur)) 1)))))
+			 (get-text-property (point) :org-include-induced-level))))
 		 (src-args (and (eq env 'literal)
 				(match-string 1 value)))
 		 (block (and (string-match "\\<\\(\\S-+\\)\\>" value)
@@ -3134,8 +3143,8 @@ storing and resolving footnotes.  It is created automatically."
 		(insert
 		 (let ((ind-str (make-string ind ? ))
 		       (arg-str (if (stringp src-args)
-				  (format " %s" src-args)
-				""))
+				    (format " %s" src-args)
+				  ""))
 		       (contents
 			(org-escape-code-in-string
 			 (org-export--prepare-file-contents file lines))))
@@ -3145,7 +3154,7 @@ storing and resolving footnotes.  It is created automatically."
 		(insert
 		 (let ((ind-str (make-string ind ? ))
 		       (contents
-			 (org-export--prepare-file-contents file lines)))
+			(org-export--prepare-file-contents file lines)))
 		   (format "%s#+BEGIN_%s\n%s%s#+END_%s\n"
 			   ind-str block contents ind-str block))))
 	       (t

testing/lisp/test-ox.el

@@ -1003,7 +1003,42 @@ Footnotes[fn:2], foot[fn:test], digit only[3], and [fn:inline:anonymous footnote
     (org-test-with-temp-text
 	(format "#+INCLUDE: \"%s/examples/include.org::#dh\" :only-contents t" org-test-dir)
       (org-export-expand-include-keyword)
-      (buffer-string)))))
+      (buffer-string))))
+  ;; Adjacent INCLUDE-keywords should have the same :minlevel if unspecified.
+  (should
+   (org-every (lambda (level) (zerop (1- level)))
+	      (org-test-with-temp-text
+		  (concat
+		   (format "#+INCLUDE: \"%s/examples/include.org::#ah\"\n" org-test-dir)
+		   (format "#+INCLUDE: \"%s/examples/include.org::*Heading\"" org-test-dir))
+		(org-export-expand-include-keyword)
+		(org-element-map (org-element-parse-buffer) 'headline
+		  (lambda (head) (org-element-property :level head))))))
+  ;; INCLUDE does not insert induced :minlevel for src-blocks.
+  (should-not
+   (equal
+    (org-test-with-temp-text
+	(format "#+INCLUDE: \"%s/examples/include2.org\" src emacs-lisp" org-test-dir)
+      (org-export-expand-include-keyword)
+      (buffer-string))
+    (org-test-with-temp-text
+	(format "#+INCLUDE: \"%s/examples/include2.org\" src emacs-lisp :minlevel 1" org-test-dir)
+      (org-export-expand-include-keyword)
+      (buffer-string))))
+  ;; INCLUDE assigns the relative :minlevel conditional on narrowing.
+  (should
+   (org-test-with-temp-text-in-file
+       (format "* h1\n<point>#+INCLUDE: \"%s/examples/include.org::#ah\"" org-test-dir)
+     (narrow-to-region (point) (point-max))
+     (org-export-expand-include-keyword)
+     (eq 1 (org-current-level))))
+  ;; If :minlevel is present do not alter it.
+  (should
+   (org-test-with-temp-text
+       (format "* h1\n<point>#+INCLUDE: \"%s/examples/include.org::#ah\" :minlevel 3" org-test-dir)
+     (narrow-to-region (point) (point-max))
+     (org-export-expand-include-keyword)
+     (eq 3 (org-current-level)))))
 
 (ert-deftest test-org-export/expand-macro ()
   "Test macro expansion in an Org buffer."