diff --git a/batch/makedist.sh b/batch/makedist.sh
index bfaaa07a67..16ef2fe05d 100755
--- a/batch/makedist.sh
+++ b/batch/makedist.sh
@@ -257,6 +257,7 @@ src/documentinfo.php
 src/documentinfoset.php
 src/documenthashmatcher.php
 src/documentrequest.php
+src/fieldchangeset.php
 src/fieldrender.php
 src/filefilter.php
 src/formatspec.php
diff --git a/src/fieldchangeset.php b/src/fieldchangeset.php
new file mode 100644
index 0000000000..97a34539ae
--- /dev/null
+++ b/src/fieldchangeset.php
@@ -0,0 +1,55 @@
+<?php
+// fieldchangeset.php -- HotCRP helper for `status:unchanged`/`status:changed`
+// Copyright (c) 2023 Eddie Kohler; see LICENSE.
+
+class FieldChangeSet {
+    /** @var array<string,1|2|3> */
+    public $_m = [];
+
+    const ABSENT = 0;
+    const UNCHANGED = 1;
+    const CHANGED = 2;
+
+    /** @param ?string $s
+     * @return $this */
+    function mark_unchanged($s) {
+        $this->apply($s, self::UNCHANGED);
+        return $this;
+    }
+
+    /** @param ?string $s
+     * @return $this */
+    function mark_changed($s) {
+        $this->apply($s, self::CHANGED);
+        return $this;
+    }
+
+    /** @param string $src
+     * @param string $dst
+     * @return $this */
+    function mark_synonym($src, $dst) {
+        $this->_m[$src] = $this->_m[$dst] =
+            ($this->_m[$src] ?? 0) | ($this->_m[$dst] ?? 0);
+        return $this;
+    }
+
+    /** @param ?string $s
+     * @param 1|2 $bit */
+    private function apply($s, $bit) {
+        foreach (explode(" ", $s ?? "") as $word) {
+            if ($word !== "") {
+                $this->_m[$word] = ($this->_m[$word] ?? 0) | $bit;
+                if (($colon = strpos($word, ":")) !== false) {
+                    $px = substr($word, 0, $colon);
+                    $this->_m[$px] = ($this->_m[$px] ?? 0) | $bit;
+                }
+            }
+        }
+    }
+
+    /** @param string $key
+     * @return 0|1|2|3 */
+    function test($key) {
+        return $this->_m[$key] ?? 0;
+    }
+}