[PATCH V3] scripts/checkpatch.pl: check for non-permalinks to Zulip

[Siddharth Menon <simeddon@gmail.com>]

Zulip links to https://rust-for-linux.zulipchat.com can break in
case of renaming the topic or channel if they are not message
links (which are permanent links).

If a non-permanent Zulip link is referenced then emit a warning
and direct the user to the Zulip documentation.

Permanent links are of the format:
https://.../#narrow/stream/x/topic/x/near/<numerical_id>

Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/Rust-for-Linux/linux/issues/1104
Signed-off-by: Siddharth Menon <simeddon@gmail.com>
---
V1->V2:
Corrected the Github link to the right issue,
Fixed grammatical errors and Replaced the link to reference 
Documentation to one that is easier to understand.
V2->V3:
Updated the URL to link directly to the section in the documentation 
with instructions on how to create perma-links.

 scripts/checkpatch.pl | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 39032224d504..58a5e02c588f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -735,6 +735,10 @@ our $obsolete_archives = qr{(?xi:
 	\Qspinics.net\E
 )};
 
+our $zulip_forums = qr{(?xi:
+	\Qrust-for-linux.zulipchat.com\E
+)};
+
 our @typeListMisordered = (
 	qr{char\s+(?:un)?signed},
 	qr{int\s+(?:(?:un)?signed\s+)?short\s},
@@ -3415,6 +3419,12 @@ sub process {
 			     "Use lore.kernel.org archive links when possible - see https://lore.kernel.org/lists.html\n" . $herecurr);
 		}
 
+# Check for permanent Zulip URL
+		if ($rawline =~ m{http.*\b$zulip_forums(?!(?:/#narrow/stream/.+/topic/.+/(?:near|with)/\d+)?($|\s+.*))}) {
+			WARN("PREFER_PERMANENT_URL",
+			     "Use permanent Zulip links when possible - see https://zulip.com/help/link-to-a-message-or-conversation#get-a-link-to-a-specific-message\n" . $herecurr);
+		}
+
 # Check for added, moved or deleted files
 		if (!$reported_maintainer_file && !$in_commit_log &&
 		    ($line =~ /^(?:new|deleted) file mode\s*\d+\s*$/ ||
-- 
2.39.2