feat(cli): Add command to export metaschema

tools/schemacode/bidsschematools/__main__.py

@@ -1,8 +1,15 @@
 import logging
 import os
+import sys
 
 import click
 
+if sys.version_info < (3, 9):
+    from importlib_resources import files
+else:
+    from importlib.resources import files
+
+
 from .schema import export_schema, load_schema
 
 
@@ -32,5 +39,19 @@ def export(ctx, schema, output):
             fobj.write(text)
 
 
+@cli.command()
+@click.option("--output", default="-")
+@click.pass_context
+def export_metaschema(ctx, output):
+    """Export BIDS schema to JSON document"""
+    metaschema = files("bidsschematools.data").joinpath("metaschema.json").read_text()
+    if output == "-":
+        print(metaschema, end="")
+    else:
+        output = os.path.abspath(output)
+        with open(output, "w") as fobj:
+            fobj.write(metaschema)
+
+
 if __name__ == "__main__":
     cli()