[ci] Guarding update date headers

Makefile

@@ -48,6 +48,7 @@ DESCRIPTION="$(shell sed -n -e "p;n;:next;/^##/Q;p;n;b next" CHANGES.md | perl -
 release:
 	@echo "Proceed to release CAISAR with release version $(TAG)? (y/n)?"
 	@read yesno; test "$$yesno" = y
+	@bash update_headers.sh
 	@echo -n $(DESCRIPTION)
 	@echo "Is the CHANGES.md correct for $(TAG) (y/n)?"
 	@read yesno; test "$$yesno" = y

update_headers.sh

 #!/usr/bin/env bash
-set -xe
+# set -xe
 NEW_DATE=$(date "+%Y")
-OLD_DATE=$(date -d '1 year ago' "+%Y")
-find . \( -type d -name .git -prune \) \( -type d -name ._build -prune \) -o -type f -print0 | xargs -0 sed -i 's/(C) '${OLD_DATE}'/(C) '${NEW_DATE}'/g'
+OLD_DATE=$(sed "5q;d" src/main.ml | awk '{print $4}')
+
\ No newline at end of file
+if [ "$OLD_DATE" != "$NEW_DATE" ]; then
+  echo "Replacing $OLD_DATE by $NEW_DATE in headers."
+  find . \( -type d -name .git -prune \) \( -type d -name ._build -prune \) -o -type f -print0 | xargs -0 sed -i 's/(C) '${OLD_DATE}'/(C) '${NEW_DATE}'/g'
+  echo "Done."
+  exit 0
+else
+  echo "Year $OLD_DATE in header src/main.ml is current date, no need to update the headers."
+  exit 0
+fi