From f2506479af3e8eac34b675582878ac783a5effda Mon Sep 17 00:00:00 2001
From: Nikolay Govorov <me@govorov.online>
Date: Fri, 24 Jul 2026 02:32:25 +0100
Subject: Linter for licenses headers

---
 README.md      |  3 ++-
 REUSE.toml     |  2 +-
 tasks/licenses | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 6e464e1..ba734bc 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,8 @@ repository cannot grant itself an exemption.
 ## Licensing policy
 
 `tasks/licenses` runs a pinned REUSE version and verifies the repository's
-licensing metadata. In Rust projects it also runs a pinned `cargo deny check`.
+licensing metadata and canonical SPDX copyright headers. In Rust projects it
+also runs a pinned `cargo deny check`.
 
 ## License
 
diff --git a/REUSE.toml b/REUSE.toml
index c87ec2f..515ecc4 100644
--- a/REUSE.toml
+++ b/REUSE.toml
@@ -7,5 +7,5 @@ version = 1
 path = [
   "README.md",
 ]
-SPDX-FileCopyrightText = "2026 Nikolay Govorov <me@govorov.online>"
+SPDX-FileCopyrightText = "2026 Nikolay Govorov"
 SPDX-License-Identifier = "CC-BY-4.0"
diff --git a/tasks/licenses b/tasks/licenses
index 538826f..cb8a932 100755
--- a/tasks/licenses
+++ b/tasks/licenses
@@ -6,6 +6,45 @@
 
 set -eu
 
+check_copyright_headers() {
+    invalid_headers=$(
+        git grep -n -I -E \
+            'Copyright[[:space:]]+(\([cC]\)|©)|SPDX-FileCopyrightText:' \
+            -- . \
+            ':(exclude)*.md' \
+            ':(exclude)LICENSE' \
+            ':(exclude)LICENSES/**' \
+            ':(exclude)COPYING*' |
+            awk 'match($0, /:[0-9]+:/) {
+                line = substr($0, RSTART + 1, RLENGTH - 2)
+                if (line > 10) {
+                    next
+                }
+
+                text = substr($0, RSTART + RLENGTH)
+                reason = ""
+                if (text ~ /^[[:space:]]*((<!--|#|\/\/|\/\*|\*)[[:space:]]*)?Copyright[[:space:]]+(\([cC]\)|©)/) {
+                    reason = "legacy copyright header"
+                } else if (text ~ /SPDX-FileCopyrightText:($|[^ ]| [[:space:]])/) {
+                    reason = "expected exactly one space after colon"
+                } else if (text ~ /SPDX-FileCopyrightText:.*Nikolay Govorov/ &&
+                           text !~ /SPDX-FileCopyrightText: 2026 Nikolay Govorov([[:space:]]*(\*\/|-->))?$/) {
+                    reason = "expected 2026 Nikolay Govorov"
+                }
+
+                if (reason != "") {
+                    print reason ": " $0
+                }
+            }'
+    )
+
+    if [ -n "$invalid_headers" ]; then
+        printf '%s\n%s\n' 'Invalid copyright headers:' "$invalid_headers" >&2
+        return 1
+    fi
+}
+
+check_copyright_headers
 reuse lint
 
 if [ -f Cargo.toml ]; then
-- 
Gilti