[bug #61422] [ms] .DS means ".DS I" after all, contradicting forthcoming documentation

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?61422>

                 Summary: [ms] .DS means ".DS I" after all, contradicting
forthcoming documentation
                 Project: GNU troff
            Submitted by: gbranden
            Submitted on: Wed 03 Nov 2021 04:43:17 PM UTC
                Category: Macro - ms
                Severity: 3 - Normal
              Item Group: Incorrect behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

Input:


.LP
Left-aligned paragraph.
.DS
This is my display.
.DE
.nr DI 2n
.DS L
Here's an explicitly left-aligned display.
.DE
.DS
And another default one\[em]convinced yet?
.DE


groff 1.22.4 output:


$ nroff -Tascii -ms EXPERIMENTS/ds.ms | cat -s

Left-aligned paragraph.

     This is my display.

Here's an explicitly left-aligned display.

  And another default one--convinced yet?



I propose to make the behavior match the documentation we've had in Git for
over a year.

Nothing in the groff 1.22.4 documentation actually says which display type is
the default; it doesn't even suggest that .DS can be called without arguments.
 Larry Kollar's ms.ms taught me that groff's default for DS is "DS L", so I
got a surprise when I tried it for myself.

I reason that "DS L" is indeed the better default because it's simpler--people
often want to turn off fill mode, and this will do it for them.  If they want
more functionality, a more expressive macro call (like "DS I" or "DS C") gets
it.

Probably want to mention this in NEWS; it's got to be on par with the mm ".MT
5" thing.




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