Prevent tests passing with old code coverage data.
If code coverage data is more than a month older than the most recent commit,
make test.py fail and request regeneration of test data.
diff --git a/tools/check_recent_coverage.sh b/tools/check_recent_coverage.sh
new file mode 100755
index 0000000..f6168a2
--- /dev/null
+++ b/tools/check_recent_coverage.sh
@@ -0,0 +1,51 @@
+#!/bin/bash
+
+# Copyright 2021, VIXL authors
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice,
+# this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+# * Neither the name of ARM Limited nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# This code coverage script assumes a Linux-like environment, and has been
+# tested on Ubuntu 18.04.
+
+COVERAGELOG="tools/code_coverage.log"
+MONTHSECONDS=$(( 60*60*24*30 ))
+
+if [ ! -f "$COVERAGELOG" ]; then
+ echo "No code coverage log found."
+ echo "Run tools/code_coverage.sh to generate one."
+ exit 2;
+fi
+
+LASTCOMMIT=`git log -1 --date=format:%s | grep -P "^Date:" | grep -Po "\d+"`
+LASTCOVERAGE=`tail -n1 $COVERAGELOG | cut -d' ' -f1`
+
+d=$(( $LASTCOMMIT - $LASTCOVERAGE ))
+if (( d < $MONTHSECONDS )); then
+ exit 0;
+fi
+
+echo "Code coverage record too old."
+echo "Run tools/code_coverage.sh to generate a newer one."
+exit 1;