Merge branch 'nd/shallow-clone'

Fetching from a shallow-cloned repository used to be forbidden,
primarily because the codepaths involved were not carefully vetted
and we did not bother supporting such usage. This attempts to allow
object transfer out of a shallow-cloned repository in a controlled
way (i.e. the receiver become a shallow repository with truncated
history).

* nd/shallow-clone: (31 commits)
  t5537: fix incorrect expectation in test case 10
  shallow: remove unused code
  send-pack.c: mark a file-local function static
  git-clone.txt: remove shallow clone limitations
  prune: clean .git/shallow after pruning objects
  clone: use git protocol for cloning shallow repo locally
  send-pack: support pushing from a shallow clone via http
  receive-pack: support pushing to a shallow clone via http
  smart-http: support shallow fetch/clone
  remote-curl: pass ref SHA-1 to fetch-pack as well
  send-pack: support pushing to a shallow clone
  receive-pack: allow pushes that update .git/shallow
  connected.c: add new variant that runs with --shallow-file
  add GIT_SHALLOW_FILE to propagate --shallow-file to subprocesses
  receive/send-pack: support pushing from a shallow clone
  receive-pack: reorder some code in unpack()
  fetch: add --update-shallow to accept refs that update .git/shallow
  upload-pack: make sure deepening preserves shallow roots
  fetch: support fetching from a shallow repository
  clone: support remote shallow repository
  ...

1 files changed, 14 insertions, 1 deletions

diff --git a/builtin/fetch.c b/builtin/fetch.c
index 09825c84d7..025bc3e38d 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -36,7 +36,7 @@ static int prune = -1; /* unspecified */
 
 static int all, append, dry_run, force, keep, multiple, update_head_ok, verbosity;
 static int progress = -1, recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
-static int tags = TAGS_DEFAULT, unshallow;
+static int tags = TAGS_DEFAULT, unshallow, update_shallow;
 static const char *depth;
 static const char *upload_pack;
 static struct strbuf default_rla = STRBUF_INIT;
@@ -105,6 +105,8 @@ static struct option builtin_fetch_options[] = {
 	{ OPTION_STRING, 0, "recurse-submodules-default",
 		   &recurse_submodules_default, NULL,
 		   N_("default mode for recursion"), PARSE_OPT_HIDDEN },
+	OPT_BOOL(0, "update-shallow", &update_shallow,
+		 N_("accept refs that update .git/shallow")),
 	OPT_END()
 };
 
@@ -524,6 +526,8 @@ static int iterate_ref_map(void *cb_data, unsigned char sha1[20])
 	struct ref **rm = cb_data;
 	struct ref *ref = *rm;
 
+	while (ref && ref->status == REF_STATUS_REJECT_SHALLOW)
+		ref = ref->next;
 	if (!ref)
 		return -1; /* end of the list */
 	*rm = ref->next;
@@ -570,6 +574,13 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 			struct ref *ref = NULL;
 			const char *merge_status_marker = "";
 
+			if (rm->status == REF_STATUS_REJECT_SHALLOW) {
+				if (want_status == FETCH_HEAD_MERGE)
+					warning(_("reject %s because shallow roots are not allowed to be updated"),
+						rm->peer_ref ? rm->peer_ref->name : rm->name);
+				continue;
+			}
+
 			commit = lookup_commit_reference_gently(rm->old_sha1, 1);
 			if (!commit)
 				rm->fetch_head_status = FETCH_HEAD_NOT_FOR_MERGE;
@@ -798,6 +809,8 @@ static struct transport *prepare_transport(struct remote *remote)
 		set_option(transport, TRANS_OPT_KEEP, "yes");
 	if (depth)
 		set_option(transport, TRANS_OPT_DEPTH, depth);
+	if (update_shallow)
+		set_option(transport, TRANS_OPT_UPDATE_SHALLOW, "yes");
 	return transport;
 }