Support batch mode

src/datalad_cds/download_cds.py

@@ -51,6 +51,13 @@ class DownloadCDS(Interface):
             doc="""target path to download to.""",
             constraints=EnsureStr(),
         ),
+        batch=Parameter(
+            args=("--batch",),
+            action="store_true",
+            doc="""By default a single request can be supplied for download.
+            With the batch option, the requests to download are instead read
+            from stdin, one request and associated filename per line.""",
+        ),
         lazy=Parameter(
             args=("--lazy",),
             action="store_true",
@@ -68,28 +75,40 @@ class DownloadCDS(Interface):
     @datasetmethod(name="download_cds")
     @eval_results
     def __call__(
-        spec: Union[str, dict],
-        path: str,
+        spec: Optional[Union[str, dict]] = None,
+        path: Optional[str] = None,
         *,
         dataset: Optional[str] = None,
         message: Optional[str] = None,
-        save: bool = True,
+        batch: bool = False,
         lazy: bool = False,
+        save: bool = True,
     ) -> Iterable[dict]:
+        ds = require_dataset(dataset, check_installed=True)
+        ensure_special_remote_exists_and_is_enabled(ds.repo, "cds")
+        if batch:
+            try:
+                next_line = input()
+                spec, path = next_line.split(" ", 1)
+                self._handle_one(ds, spec, path, batch, lazy, safe)
+            except EOFError:
+                pass
+        else:
+            self._handle_one(ds, spec, path, batch, lazy, safe)
+
+    def _handle_one(ds, spec, path, batch, lazy, safe):
         if isinstance(spec, dict):
             parsed_spec = datalad_cds.spec.Spec.from_dict(spec)
         elif isinstance(spec, str):
             parsed_spec = datalad_cds.spec.Spec.from_json(spec)
         else:
             raise TypeError("spec could not be parsed")
-        ds = require_dataset(dataset, check_installed=True)
-        ensure_special_remote_exists_and_is_enabled(ds.repo, "cds")
         pathobj = ds.pathobj / path
         url = parsed_spec.to_url()
         options = []
         if lazy:
             options.append("--fast")
-        ds.repo.add_url_to_file(pathobj, url, options=options)
+        ds.repo.add_url_to_file(pathobj, url, batch=batch, options=options)
         if save:
             msg = (
                 message