[PATCH v2] checkpatch.pl: Add check for Change-Id

[Christopher Covington <cov@codeaurora.org>]

A commit hook for the Gerrit code review server [1] inserts change
identifiers so Gerrit can track patches through multiple revisions.
These identifiers are noise in the context of the upstream kernel.
(Many Gerrit servers are private. Even given a public instance,
given only a Change-Id, one must guess which server a change was
tracked on. Patches submitted to the Linux kernel mailing lists
should be able to stand on their own. If it's truly useful to
reference code review on a Gerrit server, a URL is a much clearer
way to do so.) Thus, issue an error when a Change-Id line is
encountered before the Signed-off-by.

1. https://gerrit.googlesource.com/gerrit/+/master/gerrit-server/src/main/resources/com/google/gerrit/server/tools/root/hooks/commit-msg

Signed-off-by: Christopher Covington <cov@codeaurora.org>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 464dcef..8fad0d3 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1891,6 +1891,12 @@ sub process {
 			}
 		}
 
+# Check for unwanted Gerrit info
+		if ($in_commit_log && $line =~ /^\s*change-id:/i) {
+			ERROR("GERRIT_CHANGE_ID",
+			      "Remove Gerrit Change-Id's before submitting upstream.\n" . $herecurr);
+		}
+
 # Check for wrappage within a valid hunk of the file
 		if ($realcnt != 0 && $line !~ m{^(?:\+|-| |\\ No newline|$)}) {
 			ERROR("CORRUPTED_PATCH",
-- 
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