Org writer: always indent src blocks content by 2 spaces

Emacs always uses two spaces when indenting the content of src blocks,
e.g., when exiting a `C-c '` edit-buffer. Pandoc used to indent contents
by the space-equivalent of one tab, but now always uses two spaces, too.

Closes: #5440

src/Text/Pandoc/Writers/Org.hs

@@ -169,8 +169,6 @@ blockToOrg (Header level attr inlines) = do
                   else cr <> nest (level + 1) (propertiesDrawer attr)
   return $ headerStr <> " " <> contents <> drawerStr <> blankline
 blockToOrg (CodeBlock (_,classes,kvs) str) = do
-  opts <- gets stOptions
-  let tabstop = writerTabStop opts
   let startnum = maybe "" (\x -> ' ' : trimr x) $ lookup "startFrom" kvs
   let numberlines = if "numberLines" `elem` classes
                       then if "continuedSourceBlock" `elem` classes
@@ -181,7 +179,7 @@ blockToOrg (CodeBlock (_,classes,kvs) str) = do
   let (beg, end) = case at of
                       []    -> ("#+BEGIN_EXAMPLE" ++ numberlines, "#+END_EXAMPLE")
                       (x:_) -> ("#+BEGIN_SRC " ++ x ++ numberlines, "#+END_SRC")
-  return $ text beg $$ nest tabstop (text str) $$ text end $$ blankline
+  return $ text beg $$ nest 2 (text str) $$ text end $$ blankline
 blockToOrg (BlockQuote blocks) = do
   contents <- blockListToOrg blocks
   return $ blankline $$ "#+BEGIN_QUOTE" $$

test/command/5178.md

@@ -7,19 +7,19 @@
    unsafePerformIO main
 ^D
 #+BEGIN_SRC haskell -n 42
-    main = putStrLn "Hello World!"
+  main = putStrLn "Hello World!"
-    unsafePerformIO main
+  unsafePerformIO main
 #+END_SRC
 ```
 
 ```
 % pandoc -f org -t native
 #+BEGIN_SRC lisp -n 20
-    (+ 1 1)
+  (+ 1 1)
 #+END_SRC
 
 #+BEGIN_SRC lisp +n 10
-    (+ 2 2)
+  (+ 2 2)
 #+END_SRC
 ^D
 [CodeBlock ("",["commonlisp","numberLines"],[("org-language","lisp"),("startFrom","20")]) "(+ 1 1)\n"
@@ -32,10 +32,10 @@
 ,CodeBlock ("",["commonlisp","numberLines","continuedSourceBlock"],[("org-language","lisp"),("startFrom","10")]) "(+ 2 2)\n"]
 ^D
 #+BEGIN_SRC lisp -n 20
-    (+ 1 1)
+  (+ 1 1)
 #+END_SRC
 
 #+BEGIN_SRC lisp +n 10
-    (+ 2 2)
+  (+ 2 2)
 #+END_SRC
 ```

test/writer.org

@@ -92,9 +92,9 @@ E-mail style:
   Code in a block quote:
 
   #+BEGIN_EXAMPLE
-      sub status {
+    sub status {
-          print "working";
+        print "working";
-      }
+    }
   #+END_EXAMPLE
 
   A list:
@@ -127,21 +127,21 @@ And a following paragraph.
 Code:
 
 #+BEGIN_EXAMPLE
-    ---- (should be four hyphens)
+  ---- (should be four hyphens)
 
-    sub status {
+  sub status {
-        print "working";
+      print "working";
-    }
+  }
 
-    this code block is indented by one tab
+  this code block is indented by one tab
 #+END_EXAMPLE
 
 And:
 
 #+BEGIN_EXAMPLE
-        this code block is indented by two tabs
+      this code block is indented by two tabs
 
-    These should not be escaped:  \$ \\ \> \[ \{
+  These should not be escaped:  \$ \\ \> \[ \{
 #+END_EXAMPLE
 
 --------------
@@ -364,7 +364,7 @@ Multiple blocks with italics:
 - /orange/ :: orange fruit
 
   #+BEGIN_EXAMPLE
-      { orange code block }
+    { orange code block }
   #+END_EXAMPLE
 
   #+BEGIN_QUOTE
@@ -463,15 +463,15 @@ foo
 This should be a code block, though:
 
 #+BEGIN_EXAMPLE
-    <div>
+  <div>
-        foo
+      foo
-    </div>
+  </div>
 #+END_EXAMPLE
 
 As should this:
 
 #+BEGIN_EXAMPLE
-    <div>foo</div>
+  <div>foo</div>
 #+END_EXAMPLE
 
 Now, nested:
@@ -502,7 +502,7 @@ Multiline:
 Code block:
 
 #+BEGIN_EXAMPLE
-    <!-- Comment -->
+  <!-- Comment -->
 #+END_EXAMPLE
 
 Just plain comment, with trailing spaces on the line:
@@ -514,7 +514,7 @@ Just plain comment, with trailing spaces on the line:
 Code:
 
 #+BEGIN_EXAMPLE
-    <hr />
+  <hr />
 #+END_EXAMPLE
 
 Hr's:
@@ -751,7 +751,7 @@ Indented [[/url][thrice]].
 This should [not][] be a link.
 
 #+BEGIN_EXAMPLE
-    [not]: /url
+  [not]: /url
 #+END_EXAMPLE
 
 Foo [[/url/][bar]].
@@ -792,7 +792,7 @@ An e-mail address: [[mailto:nobody@nowhere.net][nobody@nowhere.net]]
 Auto-links should not occur here: =<http://example.com/>=
 
 #+BEGIN_EXAMPLE
-    or here: <http://example.com/>
+  or here: <http://example.com/>
 #+END_EXAMPLE
 
 --------------
@@ -837,7 +837,7 @@ This paragraph should not be part of the note, as it is not indented.
        (as with list items).
 
        #+BEGIN_EXAMPLE
-             { <code> }
+           { <code> }
        #+END_EXAMPLE
 
        If you want, you can indent every line, but you can also be lazy and