[Orgmode] Exporting blocks without removing indentation

[Dan Davison]

Fairly late in the export process, org-exp removes the common
indentation from lines inside blocks (line 2288 of org-exp.el):

(setq rtn (org-remove-indentation code))

However, what do we do if

1. A user has a block that she wishes to export with the indentation intact?

2. An org-exp-blocks plugin has a block that it wishes to export with
   the indentation intact?

I propose that we make (1) and (2) possible. An example where (1) arises
is if, when documenting a moderately complex program, different parts of
a class or function are contained in separate blocks.

Q1. Is that aim approved of?

(2) is a bit trickier than (1). To solve (1), we could introduce a fix
in org-exp.el like

-      (setq rtn (org-remove-indentation code))
+      (setq rtn (if org-src-preserve-indentation code
+                 (org-remove-indentation code)))

However in solving (2) the plugin cannot assume that the variable
org-src-preserve-indentation is in effect (in fact it very likely
isn't). So we need to come up with a way in which the block resulting
from an org-exp-blocks plugin can have its indentation survive through
to the export product, even if org-src-preserve-indentation is globally
nil. Two possibilities are

1. We adopt a convention whereby if all lines start with some character
   (say ,) then that character is removed (but the remaining indentation
   is left intact.)

2. We transplant the indentation-removing work from org-exp.el into
   org-exp-blocks.el, and arrange that it is only performed if the block
   is *not* handled by an org-exp-blocks plugin.

Q2. Has this made sense? What solution do you suggest?

Q3. Should we use org-src-preserve-indentation in this way to affect
export? (It currently has effect when switching between the org buffer
and the code edit buffer.)

Dan