On Thu, 24 Sep 2015, Nicolas Goaziou wrote:

> Hello,
>
> "Charles C. Berry" <ccberry@ucsd.edu> writes:
>
>> On Tue, 22 Sep 2015, Charles C. Berry wrote:
>>
>> Just to tie this up, this is an issue with `org-src-preserve-indentation',
>> see
>>
>>  	(info "(org) Editing source code")
>>
>> for the best documentation. I found the "replace sequences of spaces with
>> tab characters" for nil values confusing. The opposite is happening in
>> this example.
>
> Would you want to write a documentation patch about it?
>

Attached is a patch.

I think it is an improvement, but `org-src-preserve-indentation' behaves 
differently according to context, which makes it hard to document 
succinctly.

In brief:

Setting to `t' or `nil' will keep or allow removal of tabs in these 
functions:

org-babel-parse-src-block-match
org-babel-haskell-export-to-lhs
org-babel-spec-to-string
org-src--edit-element
org-edit-src-code

but have no effect on embedded tabs in

org-babel-exp-process-buffer
org-export-unravel-code
org-element-src-block-interpreter
org-element-example-block-interpreter
org-fixup-indentation

Also, as briefly noted in the doc/org.texi part of the patch global 
indent/outdent operations (e.g. org-metaright on a heading) are affected.
This might make sense but sometimes the results surprise me.

HTH,

Chuck