Add script to compile usage of experimental APIs

bin/list-experimental-api-matches.sh

@@ -0,0 +1,48 @@
+#!/bin/sh
+
+# POSIX: prefer standard grep over rg. Git is assumed present (ls-files), but
+# could be replaced with find.
+grep_experimental_apis() {
+	git ls-files packages/* lib \
+		| grep -E '\.(js|ts|jsx|tsx|php)$' \
+		| grep -v __tests__ \
+		| xargs grep -Eo '__experimental\w+'
+}
+
+# For each line as `<filepath>:<match>`, rewrite as `<package> <match>`.
+namespace() {
+	awk -F: '
+		{ print module($1), $2 }
+		function module(path) {
+			n = split(path, parts, "/")
+			if (parts[1] == "lib") return "lib"
+			return parts[1] "/" parts[2]
+		}'
+}
+
+# Like uniq, but applied across packages: if `__experimentalFoo` appears in
+# packages A and B, only keep the occurrence under A.
+compact() {
+	sort | uniq | awk '{
+		if (known_api[$2]) next
+		known_api[$2] = 1
+		print
+	}'
+}
+
+# Output a heading for each package and a link for each experimental API.
+format() {
+	awk '{
+		if (prev_dir != $1) {
+			if (NR > 1) print ""
+			printf "## `%s`\n", $1
+			prev_dir = $1
+		}
+		printf "[`%s`](/WordPress/gutenberg/search?q=%s)\n", $2, $2
+	}'
+}
+
+grep_experimental_apis \
+	| namespace \
+	| compact \
+	| format