PROBLEMS: Coalesce gdiffmk items.

Also borrow wording from "ANNOUNCE".

1 files changed, 20 insertions, 15 deletions

diff --git a/PROBLEMS b/PROBLEMS
index 8c95ae8bc..df6914c45 100644
--- a/PROBLEMS
+++ b/PROBLEMS
@@ -29,24 +29,29 @@ General Problems
 
 [groff 1.23.0]
 
-* gdiffmk doesn't work on FreeBSD; I get errors from "expr".
-
-gdiffmk uses the expr(1) command to parse its arguments.  FreeBSD has
-extended the syntax of its expr command in a non-backward compatible way
-that it claims better conforms with POSIX's utility syntax guidelines
-with respect to option processing: however, POSIX mandates no options
-for expr.  Other implementations of expr do not support traditional
-Unix-style options ('-a', '-b', ...), and perhaps as a consequence do
-not follow FreeBSD's interpretation of the guidelines.  You way want to
-set $EXPR_COMPAT in your shell environment.  We hope to have a
-workaround for this behavior in a future release.
+* gdiffmk doesn't work / its automated test fails.
 
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+Some portability issues are known to affect groff's gdiffmk utility.
 
-* gdiffmk doesn't work / its automated test fails.
+- A defect in GNU diffutils 3.9 (January 2023) causes gdiffmk to
+  malfunction and its automated test to fail.  See
+  <https://debbugs.gnu.org/db/61/61193.html>.
+
+- gdiffmk does not work with BusyBox diff (which does not implement GNU
+  diff's "-D" option).
+
+- gdiffmk does not work on FreeBSD due to specifics of that platform's
+  expr(1) implementation.
 
-A defect in GNU diffutils 3.9 (January 2023) causes gdiffmk to
-malfunction.  See <https://debbugs.gnu.org/db/61/61193.html>.
+  gdiffmk uses the expr(1) command to parse its arguments.  FreeBSD has
+  extended the syntax of its expr command in a non-backward compatible
+  way that it claims better conforms with POSIX's utility syntax
+  guidelines with respect to option processing: however, POSIX mandates
+  no options for expr.  Other implementations of expr do not support
+  traditional Unix-style options ('-a', '-b', ...), and perhaps as a
+  consequence do not follow FreeBSD's interpretation of the guidelines.
+  You way want to set $EXPR_COMPAT in your shell environment.  We hope
+  to have a workaround for this behavior in a future release.
 
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