Check that patch has dependencies update

To disable the new check, one can add NO_DEPS_UPDATE tag to the
commit message.

Author: ligurio

checkpatch.pl

@@ -500,6 +500,10 @@ sub hash_show_words {
 	NO_CHANGELOG
 )};
 
+our $custom_tags_no_reason = qr{(?x:
+	NO_DEPS_UPDATE
+)};
+
 our $github_ref = qr{(https?:\/\/)?(www\.)?github\.com\b([-a-zA-Z0-9()@:%_\+.~\#?&\/=]*)};
 our $github_issue_ref = qr{((tarantool\/\S+)?\#[1-9][0-9]*)};
 
@@ -2156,6 +2160,7 @@ sub process {
 	my $new_file = 0;
 	my $has_doc = 0;
 	my $has_test = 0;
+	my $need_deps_update = 0;
 	my $is_test = 0;
 
 	# Pre-scan the patch sanitizing the lines.
@@ -2747,7 +2752,8 @@ sub process {
 			}
 		}
 
-		if ($in_commit_log && $line =~ /^($custom_tags)=/) {
+		if ($in_commit_log && ($line =~ /^($custom_tags)=/ ||
+		    $line =~ /^($custom_tags_no_reason)$/)) {
 			$commit_log_tags{$1} = 1;
 			if ($has_doc) {
 				ERROR("TAG_IN_DOC",
@@ -2767,6 +2773,9 @@ sub process {
 		if ($realfile =~ /^(?:static-build\/)?test\/.*\//) {
 			$has_test = 1;
 		}
+		if ($realfile =~ /^(?:third_party|cmake)\//) {
+			$need_deps_update = 1;
+		}
 
 		$is_test = ($realfile =~ /^(?:test|perf)\//);
 
@@ -5293,6 +5302,11 @@ sub process {
 			ERROR("NO_TEST",
 			      "Please add test or NO_TEST=<reason> tag\n");
 		}
+		if ($need_deps_update && !exists($commit_log_tags{'NO_DEPS_UPDATE'}) &&
+		    !($filename !~ /^extra\/dependencies\.yaml$/)) {
+			ERROR("NO_DEPS_UPDATE",
+			      "Please update extra/dependencies.yaml or add NO_DEPS_UPDATE tag\n");
+		}
 	}
 
 	print report_dump();

doc/checkpatch.rst

@@ -766,6 +766,13 @@ Others
     If the patch doesn't need a test (e.g. it fixes a CI issue), please add
     NO_TEST=<reason> to the commit log.
 
+  **NO_DEPS_UPDATE**
+    The patch updates files that may describe external dependencies of the
+    project.  If it does introduce a new build dependency or updates the version
+    of an existing build dependency, please update extra/dependencies.yaml
+    accordingly, otherwise add NO_DEPS_UPDATE to the commit log to suppress
+    this warning.
+
   **NOT_UNIFIED_DIFF**
     The patch file does not appear to be in unified-diff format.  Please
     regenerate the patch file before sending it to the maintainer.