--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/contrib/check-compat-strings.sh	Fri May 08 22:50:09 2020 +0800
@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+unset GREP_OPTIONS
+
+# This script finds compatibility-related comments with a node hash specified
+# in all files in a given directory (. by default) and looks up the hash in a
+# repo (~/hg by default) to determine if each of the comments is correct and,
+# if not, it suggests the correct release. This can prevent accidentally
+# removing a piece of code that was misattributed to a different (earlier)
+# release of core hg.
+
+# Usage: $0 WDIR HGREPO where WDIR is usually evolve/hgext3rd/ and HGREPO is
+# the place with core Mercurial repo (not just checkout). Said repo has to be
+# sufficiently up-to-date, otherwise this script may not work correctly.
+
+workdir=${1:-'.'}
+hgdir=${2:-~/hg}
+grep -Ern 'hg <= [0-9.]+ \([0-9a-f+]+\)' "$workdir" | while read -r line; do
+    bashre='hg <= ([0-9.]+) \(([0-9a-f+]+)\)'
+    if [[ $line =~ $bashre ]]; then
+        expected=${BASH_REMATCH[1]}
+        revset=${BASH_REMATCH[2]}
+        tagrevset="max(tag('re:^[0-9]\\.[0-9]$') - ($revset)::)"
+        lastrel=$(HGPLAIN=1 hg --cwd "$hgdir" log -r "$tagrevset" -T '{tags}')
+        if [[ "$lastrel" != "$expected" ]]; then
+            echo "$line"
+            echo "actual last major release without $revset is $lastrel"
+            echo
+        fi
+    fi
+done