upload-pack: send refs' objects despite "filter"

A filter line in a request to upload-pack filters out objects regardless
of whether they are directly referenced by a "want" line or not. This
means that cloning with "--filter=blob:none" (or another filter that
excludes blobs) from a repository with at least one ref pointing to a
blob (for example, the Git repository itself) results in output like the
following:

    error: missing object referenced by 'refs/tags/junio-gpg-pub'

and if that particular blob is not referenced by a fetched tree, the
resulting clone fails fsck because there is no object from the remote to
vouch that the missing object is a promisor object.

Update both the protocol and the upload-pack implementation to include
all explicitly specified "want" objects in the packfile regardless of
the filter specification.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/pack-protocol.txt

@@ -284,7 +284,9 @@ information is sent back to the client in the next step.
 The client can optionally request that pack-objects omit various
 objects from the packfile using one of several filtering techniques.
 These are intended for use with partial clone and partial fetch
-operations.  See `rev-list` for possible "filter-spec" values.
+operations. An object that does not meet a filter-spec value is
+omitted unless explicitly requested in a 'want' line. See `rev-list`
+for possible filter-spec values.
 
 Once all the 'want's and 'shallow's (and optional 'deepen') are
 transferred, clients MUST send a flush-pkt, to tell the server side

list-objects.c

@@ -47,7 +47,7 @@ static void process_blob(struct rev_info *revs,
 
 	pathlen = path->len;
 	strbuf_addstr(path, name);
-	if (filter_fn)
+	if (!(obj->flags & USER_GIVEN) && filter_fn)
 		r = filter_fn(LOFS_BLOB, obj,
 			      path->buf, &path->buf[pathlen],
 			      filter_data);
@@ -132,7 +132,7 @@ static void process_tree(struct rev_info *revs,
 	}
 
 	strbuf_addstr(base, name);
-	if (filter_fn)
+	if (!(obj->flags & USER_GIVEN) && filter_fn)
 		r = filter_fn(LOFS_BEGIN_TREE, obj,
 			      base->buf, &base->buf[baselen],
 			      filter_data);
@@ -171,7 +171,7 @@ static void process_tree(struct rev_info *revs,
 				     cb_data, filter_fn, filter_data);
 	}
 
-	if (filter_fn) {
+	if (!(obj->flags & USER_GIVEN) && filter_fn) {
 		r = filter_fn(LOFS_END_TREE, obj,
 			      base->buf, &base->buf[baselen],
 			      filter_data);

object.h

@@ -27,7 +27,7 @@ struct object_array {
 
 /*
  * object flag allocation:
- * revision.h:               0---------10                                26
+ * revision.h:               0---------10                              2526
  * fetch-pack.c:             0----5
  * walker.c:                 0-2
  * upload-pack.c:                4       11----------------19

revision.c

@@ -172,6 +172,7 @@ static void add_pending_object_with_path(struct rev_info *revs,
 		strbuf_release(&buf);
 		return; /* do not add the commit itself */
 	}
+	obj->flags |= USER_GIVEN;
 	add_object_array_with_path(obj, name, &revs->pending, mode, path);
 }
 

revision.h

@@ -19,8 +19,9 @@
 #define SYMMETRIC_LEFT	(1u<<8)
 #define PATCHSAME	(1u<<9)
 #define BOTTOM		(1u<<10)
+#define USER_GIVEN	(1u<<25) /* given directly by the user */
 #define TRACK_LINEAR	(1u<<26)
-#define ALL_REV_FLAGS	(((1u<<11)-1) | TRACK_LINEAR)
+#define ALL_REV_FLAGS	(((1u<<11)-1) | USER_GIVEN | TRACK_LINEAR)
 
 #define DECORATE_SHORT_REFS	1
 #define DECORATE_FULL_REFS	2

t/t5317-pack-objects-filter-objects.sh

@@ -160,6 +160,22 @@ test_expect_success 'verify blob:limit=1k' '
 	test_cmp observed expected
 '
 
+test_expect_success 'verify explicitly specifying oversized blob in input' '
+	git -C r2 ls-files -s large.1000 large.10000 \
+		| awk -f print_2.awk \
+		| sort >expected &&
+	git -C r2 pack-objects --rev --stdout --filter=blob:limit=1k >filter.pack <<-EOF &&
+	HEAD
+	$(git -C r2 rev-parse HEAD:large.10000)
+	EOF
+	git -C r2 index-pack ../filter.pack &&
+	git -C r2 verify-pack -v ../filter.pack \
+		| grep blob \
+		| awk -f print_1.awk \
+		| sort >observed &&
+	test_cmp observed expected
+'
+
 test_expect_success 'verify blob:limit=1m' '
 	git -C r2 ls-files -s large.1000 large.10000 \
 		| awk -f print_2.awk \

t/t5616-partial-clone.sh

@@ -154,4 +154,20 @@ test_expect_success 'partial clone with transfer.fsckobjects=1 uses index-pack -
 	grep "git index-pack.*--fsck-objects" trace
 '
 
+test_expect_success 'partial clone fetches blobs pointed to by refs even if normally filtered out' '
+	rm -rf src dst &&
+	git init src &&
+	test_commit -C src x &&
+	test_config -C src uploadpack.allowfilter 1 &&
+	test_config -C src uploadpack.allowanysha1inwant 1 &&
+
+	# Create a tag pointing to a blob.
+	BLOB=$(echo blob-contents | git -C src hash-object --stdin -w) &&
+	git -C src tag myblob "$BLOB" &&
+
+	git clone --filter="blob:none" "file://$(pwd)/src" dst 2>err &&
+	! grep "does not point to a valid object" err &&
+	git -C dst fsck
+'
+
 test_done