Merge branch 'jt/lazy-fetch'

Updates to on-demand fetching code in lazily cloned repositories.

* jt/lazy-fetch:
  fetch: no FETCH_HEAD display if --no-write-fetch-head
  fetch-pack: remove no_dependents code
  promisor-remote: lazy-fetch objects in subprocess
  fetch-pack: do not lazy-fetch during ref iteration
  fetch: only populate existing_refs if needed
  fetch: avoid reading submodule config until needed
  fetch: allow refspecs specified through stdin
  negotiator/noop: add noop fetch negotiator

fetch-pack.h

@@ -50,20 +50,6 @@ struct fetch_pack_args {
 	 */
 	unsigned from_promisor:1;
 
-	/*
-	 * Attempt to fetch only the wanted objects, and not any objects
-	 * referred to by them. Due to protocol limitations, extraneous
-	 * objects may still be included. (When fetching non-blob
-	 * objects, only blobs are excluded; when fetching a blob, the
-	 * blob itself will still be sent. The client does not need to
-	 * know whether a wanted object is a blob or not.)
-	 *
-	 * If 1, fetch_pack() will also not modify any object flags.
-	 * This allows fetch_pack() to safely be called by any function,
-	 * regardless of which object flags it uses (if any).
-	 */
-	unsigned no_dependents:1;
-
 	/*
 	 * Because fetch_pack() overwrites the shallow file upon a
 	 * successful deepening non-clone fetch, if this struct