Format JSON, include CI check (#7071)

scripts/lint-json.sh

@@ -0,0 +1,45 @@
+#!/bin/sh
+# Lint JSON in soh/assets/custom: each file must parse and be formatted like
+# `jq --indent 4` prints it, same 4-space indentation game writes presets with.
+#
+#   scripts/lint-json.sh          # check, non-zero exit on any problem
+#   scripts/lint-json.sh --fix    # reformat in place
+#
+# Comments not allowed even though resource manager parses with ignore_comments.
+#
+# Python's json.tool is used when jq is missing.
+
+cd "$(dirname "$0")/.." || exit 2
+
+if command -v jq > /dev/null; then
+    format() { jq --indent 4 . "$1"; }
+elif python=$(command -v python3 || command -v python); then
+    format() { "$python" -m json.tool --indent 4 --no-ensure-ascii "$1"; }
+else
+    echo "needs jq or python 3.9+"
+    exit 2
+fi
+
+find soh/assets/custom -name '*.json' | LC_ALL=C sort | {
+    status=0
+    count=0
+    while IFS= read -r file; do
+        count=$((count + 1))
+        if ! formatted=$(format "$file" 2>&1); then
+            printf '%s: %s\n' "$file" "$formatted"  # printf: dash's echo eats backslashes
+            status=1
+        elif diff=$(printf '%s\n' "$formatted" | diff -u "$file" -); then
+            continue
+        elif [ "$1" = "--fix" ]; then
+            printf '%s\n' "$formatted" > "$file"
+            echo "fixed $file"
+        else
+            printf '%s\n' "$diff"
+            status=1
+        fi
+    done
+
+    [ "$count" -gt 0 ] || { echo "found no JSON under soh/assets/custom"; exit 2; }
+    [ "$status" = 0 ] || echo "run scripts/lint-json.sh --fix to reformat"
+    exit "$status"
+}