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, 119 insertions, 12 deletions

diff --git a/fetch-pack.c b/fetch-pack.c
index 760ed16e79..d52de74c4b 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -13,6 +13,7 @@
 #include "transport.h"
 #include "version.h"
 #include "prio-queue.h"
+#include "sha1-array.h"
 
 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
@@ -309,7 +310,7 @@ static int find_common(struct fetch_pack_args *args,
 	}
 
 	if (is_repository_shallow())
-		write_shallow_commits(&req_buf, 1);
+		write_shallow_commits(&req_buf, 1, NULL);
 	if (args->depth > 0)
 		packet_buf_write(&req_buf, "deepen %d", args->depth);
 	packet_buf_flush(&req_buf);
@@ -772,6 +773,7 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 				 int fd[2],
 				 const struct ref *orig_ref,
 				 struct ref **sought, int nr_sought,
+				 struct shallow_info *si,
 				 char **pack_lockfile)
 {
 	struct ref *ref = copy_ref_list(orig_ref);
@@ -848,7 +850,10 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (args->stateless_rpc)
 		packet_flush(fd[1]);
 	if (args->depth > 0)
-		setup_alternate_shallow(&shallow_lock, &alternate_shallow_file);
+		setup_alternate_shallow(&shallow_lock, &alternate_shallow_file,
+					NULL);
+	else if (si->nr_ours || si->nr_theirs)
+		alternate_shallow_file = setup_temporary_shallow(si->shallow);
 	else
 		alternate_shallow_file = NULL;
 	if (get_pack(args, fd, pack_lockfile))
@@ -922,14 +927,121 @@ static int remove_duplicates_in_refs(struct ref **ref, int nr)
 	return dst;
 }
 
+static void update_shallow(struct fetch_pack_args *args,
+			   struct ref **sought, int nr_sought,
+			   struct shallow_info *si)
+{
+	struct sha1_array ref = SHA1_ARRAY_INIT;
+	int *status;
+	int i;
+
+	if (args->depth > 0 && alternate_shallow_file) {
+		if (*alternate_shallow_file == '\0') { /* --unshallow */
+			unlink_or_warn(git_path("shallow"));
+			rollback_lock_file(&shallow_lock);
+		} else
+			commit_lock_file(&shallow_lock);
+		return;
+	}
+
+	if (!si->shallow || !si->shallow->nr)
+		return;
+
+	if (alternate_shallow_file) {
+		/*
+		 * The temporary shallow file is only useful for
+		 * index-pack and unpack-objects because it may
+		 * contain more roots than we want. Delete it.
+		 */
+		if (*alternate_shallow_file)
+			unlink(alternate_shallow_file);
+		free((char *)alternate_shallow_file);
+	}
+
+	if (args->cloning) {
+		/*
+		 * remote is shallow, but this is a clone, there are
+		 * no objects in repo to worry about. Accept any
+		 * shallow points that exist in the pack (iow in repo
+		 * after get_pack() and reprepare_packed_git())
+		 */
+		struct sha1_array extra = SHA1_ARRAY_INIT;
+		unsigned char (*sha1)[20] = si->shallow->sha1;
+		for (i = 0; i < si->shallow->nr; i++)
+			if (has_sha1_file(sha1[i]))
+				sha1_array_append(&extra, sha1[i]);
+		if (extra.nr) {
+			setup_alternate_shallow(&shallow_lock,
+						&alternate_shallow_file,
+						&extra);
+			commit_lock_file(&shallow_lock);
+		}
+		sha1_array_clear(&extra);
+		return;
+	}
+
+	if (!si->nr_ours && !si->nr_theirs)
+		return;
+
+	remove_nonexistent_theirs_shallow(si);
+	if (!si->nr_ours && !si->nr_theirs)
+		return;
+	for (i = 0; i < nr_sought; i++)
+		sha1_array_append(&ref, sought[i]->old_sha1);
+	si->ref = &ref;
+
+	if (args->update_shallow) {
+		/*
+		 * remote is also shallow, .git/shallow may be updated
+		 * so all refs can be accepted. Make sure we only add
+		 * shallow roots that are actually reachable from new
+		 * refs.
+		 */
+		struct sha1_array extra = SHA1_ARRAY_INIT;
+		unsigned char (*sha1)[20] = si->shallow->sha1;
+		assign_shallow_commits_to_refs(si, NULL, NULL);
+		if (!si->nr_ours && !si->nr_theirs) {
+			sha1_array_clear(&ref);
+			return;
+		}
+		for (i = 0; i < si->nr_ours; i++)
+			sha1_array_append(&extra, sha1[si->ours[i]]);
+		for (i = 0; i < si->nr_theirs; i++)
+			sha1_array_append(&extra, sha1[si->theirs[i]]);
+		setup_alternate_shallow(&shallow_lock,
+					&alternate_shallow_file,
+					&extra);
+		commit_lock_file(&shallow_lock);
+		sha1_array_clear(&extra);
+		sha1_array_clear(&ref);
+		return;
+	}
+
+	/*
+	 * remote is also shallow, check what ref is safe to update
+	 * without updating .git/shallow
+	 */
+	status = xcalloc(nr_sought, sizeof(*status));
+	assign_shallow_commits_to_refs(si, NULL, status);
+	if (si->nr_ours || si->nr_theirs) {
+		for (i = 0; i < nr_sought; i++)
+			if (status[i])
+				sought[i]->status = REF_STATUS_REJECT_SHALLOW;
+	}
+	free(status);
+	sha1_array_clear(&ref);
+}
+
 struct ref *fetch_pack(struct fetch_pack_args *args,
 		       int fd[], struct child_process *conn,
 		       const struct ref *ref,
 		       const char *dest,
 		       struct ref **sought, int nr_sought,
+		       struct sha1_array *shallow,
 		       char **pack_lockfile)
 {
 	struct ref *ref_cpy;
+	struct shallow_info si;
 
 	fetch_pack_setup();
 	if (nr_sought)
@@ -939,16 +1051,11 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		packet_flush(fd[1]);
 		die("no matching remote head");
 	}
-	ref_cpy = do_fetch_pack(args, fd, ref, sought, nr_sought, pack_lockfile);
-
-	if (args->depth > 0 && alternate_shallow_file) {
-		if (*alternate_shallow_file == '\0') { /* --unshallow */
-			unlink_or_warn(git_path("shallow"));
-			rollback_lock_file(&shallow_lock);
-		} else
-			commit_lock_file(&shallow_lock);
-	}
-
+	prepare_shallow_info(&si, shallow);
+	ref_cpy = do_fetch_pack(args, fd, ref, sought, nr_sought,
+				&si, pack_lockfile);
 	reprepare_packed_git();
+	update_shallow(args, sought, nr_sought, &si);
+	clear_shallow_info(&si);
 	return ref_cpy;
 }