[man]: Improve portability of a test.

* tmac/tests/an_TS-do-not-keep-tables-when-cR-set.sh: Improve
  portability of script by using shell constructs instead of the
  nonstandard GNU coreutils 'seq' utility.  Resolves test failure on
  Solaris 10.

* HACKING: Document this problem.

ChangeLog

@@ -1,3 +1,11 @@
+2023-02-20  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+	* tmac/tests/an_TS-do-not-keep-tables-when-cR-set.sh: Improve
+	portability of script by using shell constructs instead of the
+	nonstandard GNU coreutils 'seq' utility.  Resolves test failure
+	on Solaris 10.
+	* HACKING: Document this problem.
+
 2023-02-20  G. Branden Robinson <g.branden.robinson@gmail.com>
 
 	* m4/groff.m4 (GROFF_MAKE_DEFINES_RM): Test the make(1) in the

HACKING

@@ -83,6 +83,15 @@ Here are some portability notes on writing automated tests.
   available at the Open Group's web site.
     https://pubs.opengroup.org/onlinepubs/009656399/toc.pdf
 
+* The GNU coreutils "seq" command is handy but not standardized by
+  POSIX.  Replace it with a while loop.
+
+    seq 53
+    n=1; while [ $n -le 53 ]; do echo $n; n=$(( n + 1 )); done
+
+  "unset" is supported by POSIX-conformant shell; use it to remove
+  temporary shell variables after use.
+
 * The "od" command on macOS can put extra space characters (i.e., spaces
   that don't correspond to the input) at the ends of lines when using
   the "od -t c" format; GNU od does not.

tmac/tests/an_TS-do-not-keep-tables-when-cR-set.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 #
-# Copyright (C) 2020 Free Software Foundation, Inc.
+# Copyright (C) 2020-2023 Free Software Foundation, Inc.
 #
 # This file is part of groff.
 #
@@ -42,7 +42,7 @@ is set.
 .
 .TS
 l.
-'$(seq 53)'
+'$(n=1; while [ $n -le 53 ]; do echo $n; n=$(( n + 1 )); done)'
 .TE'
 
 OUTPUT=$(printf "%s\n" "$EXAMPLE" | "$groff" -Tascii -P-cbou -t -man)