Add check for missing or duplicate newlines at the end of files

.github/workflows/checks.yml

@@ -16,6 +16,7 @@ jobs:
       matrix:
         check: [
           "check_format",
+          "check_newlines",
           "tests",
           "tests_coverage",
           "px4_fmu-v2_default stack_check",

Makefile

@@ -379,9 +379,9 @@ doxygen:
 	@$(PX4_MAKE) -C "$(SRC_DIR)"/build/doxygen
 	@touch "$(SRC_DIR)"/build/doxygen/Documentation/.nojekyll
 
-# Astyle
+# Style
 # --------------------------------------------------------------------
-.PHONY: check_format format
+.PHONY: check_format format check_newlines
 
 check_format:
 	$(call colorecho,'Checking formatting with astyle')
@@ -392,6 +392,10 @@ format:
 	$(call colorecho,'Formatting with astyle')
 	@"$(SRC_DIR)"/Tools/astyle/check_code_style_all.sh --fix
 
+check_newlines:
+	$(call colorecho,'Checking for missing or duplicate newlines at the end of files')
+	@"$(SRC_DIR)"/Tools/astyle/check_newlines.sh
+
 # Testing
 # --------------------------------------------------------------------
 .PHONY: tests tests_coverage tests_mission tests_mission_coverage tests_offboard tests_avoidance

Tools/astyle/check_newlines.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+return_value=0
+
+# Check if there are files checked in that don't end in a newline (POSIX requirement)
+git grep --cached -Il '' | xargs -L1 bash -c 'if test "$(tail -c 1 "$0")"; then echo "No new line at end of $0"; exit 1; fi'
+
+if [ $? -ne 0 ]; then
+	return_value=1
+fi
+
+# Check if there are files checked in that have duplicate newlines at the end (fail trailing whitespace checks)
+git grep --cached -Il '' | xargs -L1 bash -c 'if tail -c 2 "$0" | ( read x && read y && [ x"$x" = x ] && [ x"$y" = x ]); then echo "Multiple newlines at the end of $0"; exit 1; fi'
+
+if [ $? -ne 0 ]; then
+	return_value=1
+fi
+
+exit $return_value