Re: [9front] patch: import replacement for ape/patch

[Humm <hummsmith42@gmail.com>]

Quoth Amavect:
>On Mon, 23 May 2022 12:57:23 +0000
>Humm <hummsmith42@gmail.com> wrote:
>
>> >Content-Type: application/x-troff-man
>>
>> text/troff exists.
>
>A man page is a specific kind of troff file.

Quoting RFC4263:

>Optional parameters:
>[…]
>  process: Human-readable additional information for formatting,
>     including environment variables, preprocessor arguments and
>     order, formatter arguments, and postprocessors.  The parameter
>     value may need to be quoted or encoded as provided for by
>     [N4.RFC2045] as amended by [N5.RFC2231] and [N6.Errata].
>     Generating implementations must not encode executable content
>     and other implementations must not attempt any execution or
>     other interpretation of the parameter value, as the parameter
>     value may be prose text.  Implementations SHOULD present the
>     parameter (after reassembly of continuation parameters, etc.)
>     as information related to the media type, particularly if the
>     media content is not immediately available (e.g., as with
>     message/external-body composite media [N3.RFC2046]).

As examples are provided:

	text/troff ; process="dformat | pic -n | troff -ms"

and

	text/troff ; process="use pic -n then troff -ms"

>(do mime types even matter?)

Yes.  Well-behaved MUAs decide what to do with stuff by looking at 
those.

For troff: No.

>> In troff, blank lines are UB.  They should be removed or replaced by
>> lines with just a period.
>>
>
>Is that true? I'm having trouble finding a reference.

While much documentation for specific troffs indeed says that blank 
lines have the same effect as `.sp 1`—they do implement that, after 
all—that behavior is not ubiquitous.  A warning is given, for example, 
by mandoc.  Quoting mandoc(1):

>blank line in fill mode, using .sp
>  (mdoc) The meaning of blank input lines is only well-defined in 
>  non-fill mode: In fill mode, line breaks of text input lines are not 
>  supposed to be significant.  However, for compatibility with groff, 
>  blank lines in fill mode are formatted like sp requests.  To request 
>  a paragraph break, use Pp instead of a blank line.

>https://www.gnu.org/software/groff/manual/html_node/Basics.html
>Sometimes a new output line should be started even though the current
>line is not yet full; for example, at the end of a paragraph. To do
>this it is possible to cause a break, which starts a new output line.
>Some requests cause a break automatically, as normally do blank input
>lines and input lines beginning with a space.

The groff docs are obnoxious in not telling you what is extension and 
what not or how portable something is.

-- 
Humm