seq: give better diagnostics for invalid formats.

* src/seq.c: (validate_format): New function.
(main): Use it.
* tests/misc/seq (fmt-d, fmt-e): Test for expected diagnostics with
invalid formats.
* NEWS: Mention this change.
* TODO: Remove this item.
[jm: src/seq.c: make diagnostics more consistent
 tests/misc/seq (fmt-eos1): adjust the expected diagnostic ]

1 files changed, 2 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index daa5633b6..233e514d3 100644
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 
   ls --color no longer outputs unnecessary escape sequences
 
+  seq gives better diagnostics for invalid formats.
+
 ** Consistency
 
   mkdir and split now write --verbose output to stdout, not stderr.