Force ragged-right justification with groff 1.23.0

groff 1.23.0 added code to the an macro underlying .IP and .TP that
resets the justification to the AD register, which defaults to b
(full justification). Pod::Man attempts to force ragged-right
justification under nroff with .if n .ad l after .TH, but that change
was reverted in the first =item list, resulting in strange-looking
formatted manual pages in a terminal.

Work around this by setting the AD string to l if the formatter is
nroff in the preamble of each page. This undermines the intended
upstream use of AD as a way for the user to override the formatting,
but Pod::Man-generated man pages already didn't support that and
there currently is no clean way to support the AD string while still
changing the default under nroff to ragged-right justification, as has
been the practice of Pod::Man since its first release in 1999.

Fixes #23

Changes

@@ -32,6 +32,10 @@ v6.0.0 - Not Released
    at build time.  Thanks to Marco Sirabella for the analysis and an
    initial patch.  (GitHub #21)
 
+ - Add a workaround to Pod::Man to force persistent ragged-right
+   justification under nroff with groff 1.23.0.  Thanks to Guillem Jover
+   for the report and G. Branden Robinson for the analysis.  (GitHub #23)
+
  - Fix wrapping of text with S<> markup in all subclasses of Pod::Text.
    Thanks to Jim Avera for the report.  (GitHub #24)
 

THANKS

@@ -197,9 +197,10 @@ title of a simple module and for how best to suppress Encode warnings
 during Perl core builds.
 
 Guillem Jover, for the formatting change for manual page references and
-function names to match the Linux manual page standard, and reporting a
+function names to match the Linux manual page standard, reporting a
 diagnostic bug when pod2man or pod2text gets empty input on standard
-input.
+input, and reporting a groff 1.23.0 regression with ragged-right
+justification.
 
 Zefram, for analyzing and fixing a problem with the UTF-8 layer detection
 code in Pod::Man.
@@ -237,7 +238,8 @@ continued farther than they should in Pod::Man output if they were
 combined with C<> and fixed-width fonts, and for finding a subtle spacing
 bug with nested =items without bodies.
 
-G. Branden Robinson, for his assistance in understanding *roff syntax.
+G. Branden Robinson, for his assistance in understanding *roff syntax and
+analysis of groff justification changes.
 
 youpong, for reporting a double-encoding bug with a :utf8 output layer.
 

lib/Pod/Man.pm

@@ -1620,6 +1620,9 @@ sub preamble_template {
 .    \}
 .\}
 .rr rF
+.\"
+.\" Required to disable full justification in groff 1.23.0.
+.if n .ds AD l
 ----END OF PREAMBLE----
 
     if ($$self{ENCODING} eq 'roff') {

t/data/man/encoding.groff

@@ -50,6 +50,9 @@
 .    \}
 .\}
 .rr rF
+.\"
+.\" Required to disable full justification in groff 1.23.0.
+.if n .ds AD l
 .\" ========================================================================
 .\"
 .IX Title "ENCODING 1"

t/data/man/encoding.roff

@@ -51,6 +51,9 @@
 .\}
 .rr rF
 .\"
+.\" Required to disable full justification in groff 1.23.0.
+.if n .ds AD l
+.\"
 .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
 .\" Fear.  Run.  Save yourself.  No user-serviceable parts.
 .    \" fudge factors for nroff and troff

t/data/man/encoding.utf8

@@ -51,6 +51,9 @@
 .    \}
 .\}
 .rr rF
+.\"
+.\" Required to disable full justification in groff 1.23.0.
+.if n .ds AD l
 .\" ========================================================================
 .\"
 .IX Title "ENCODING 1"