Merge branch 'md/filter-trees'

The "rev-list --filter" feature learned to exclude all trees via
"tree:0" filter.

* md/filter-trees:
  list-objects: support for skipping tree traversal
  filter-trees: code clean-up of tests
  list-objects-filter: implement filter tree:0
  list-objects-filter-options: do not over-strbuf_init
  list-objects-filter: use BUG rather than die
  revision: mark non-user-given objects instead
  rev-list: handle missing tree objects properly
  list-objects: always parse trees gently
  list-objects: refactor to process_tree_contents
  list-objects: store common func args in struct

13 files changed, 433 insertions, 128 deletions

diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index 7b273635de..5f1672913b 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -731,6 +731,11 @@ the requested refs.
 +
 The form '--filter=sparse:path=<path>' similarly uses a sparse-checkout
 specification contained in <path>.
++
+The form '--filter=tree:<depth>' omits all blobs and trees whose depth
+from the root tree is >= <depth> (minimum depth if an object is located
+at multiple depths in the commits traversed). Currently, only <depth>=0
+is supported, which omits all blobs and trees.
 
 --no-filter::
 	Turn off any previous `--filter=` argument.
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index cc1b70522f..5064d08e1b 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -6,6 +6,7 @@
 #include "list-objects.h"
 #include "list-objects-filter.h"
 #include "list-objects-filter-options.h"
+#include "object.h"
 #include "object-store.h"
 #include "pack.h"
 #include "pack-bitmap.h"
@@ -209,7 +210,8 @@ static inline void finish_object__ma(struct object *obj)
 	 */
 	switch (arg_missing_action) {
 	case MA_ERROR:
-		die("missing blob object '%s'", oid_to_hex(&obj->oid));
+		die("missing %s object '%s'",
+		    type_name(obj->type), oid_to_hex(&obj->oid));
 		return;
 
 	case MA_ALLOW_ANY:
@@ -222,8 +224,8 @@ static inline void finish_object__ma(struct object *obj)
 	case MA_ALLOW_PROMISOR:
 		if (is_promisor_object(&obj->oid))
 			return;
-		die("unexpected missing blob object '%s'",
-		    oid_to_hex(&obj->oid));
+		die("unexpected missing %s object '%s'",
+		    type_name(obj->type), oid_to_hex(&obj->oid));
 		return;
 
 	default:
@@ -235,7 +237,7 @@ static inline void finish_object__ma(struct object *obj)
 static int finish_object(struct object *obj, const char *name, void *cb_data)
 {
 	struct rev_list_info *info = cb_data;
-	if (obj->type == OBJ_BLOB && !has_object_file(&obj->oid)) {
+	if (!has_object_file(&obj->oid)) {
 		finish_object__ma(obj);
 		return 1;
 	}
@@ -373,6 +375,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	repo_init_revisions(the_repository, &revs, prefix);
 	revs.abbrev = DEFAULT_ABBREV;
 	revs.commit_format = CMIT_FMT_UNSPECIFIED;
+	revs.do_not_die_on_missing_tree = 1;
 
 	/*
 	 * Scan the argument list before invoking setup_revisions(), so that we
diff --git a/list-objects-filter-options.c b/list-objects-filter-options.c
index c0e2bd6a06..e8da2e8581 100644
--- a/list-objects-filter-options.c
+++ b/list-objects-filter-options.c
@@ -30,7 +30,6 @@ static int gently_parse_list_objects_filter(
 
 	if (filter_options->choice) {
 		if (errbuf) {
-			strbuf_init(errbuf, 0);
 			strbuf_addstr(
 				errbuf,
 				_("multiple filter-specs cannot be combined"));
@@ -50,6 +49,19 @@ static int gently_parse_list_objects_filter(
 			return 0;
 		}
 
+	} else if (skip_prefix(arg, "tree:", &v0)) {
+		unsigned long depth;
+		if (!git_parse_ulong(v0, &depth) || depth != 0) {
+			if (errbuf) {
+				strbuf_addstr(
+					errbuf,
+					_("only 'tree:0' is supported"));
+			}
+			return 1;
+		}
+		filter_options->choice = LOFC_TREE_NONE;
+		return 0;
+
 	} else if (skip_prefix(arg, "sparse:oid=", &v0)) {
 		struct object_context oc;
 		struct object_id sparse_oid;
@@ -71,10 +83,9 @@ static int gently_parse_list_objects_filter(
 		return 0;
 	}
 
-	if (errbuf) {
-		strbuf_init(errbuf, 0);
+	if (errbuf)
 		strbuf_addf(errbuf, "invalid filter-spec '%s'", arg);
-	}
+
 	memset(filter_options, 0, sizeof(*filter_options));
 	return 1;
 }
diff --git a/list-objects-filter-options.h b/list-objects-filter-options.h
index 0000a61f82..af64e5c66f 100644
--- a/list-objects-filter-options.h
+++ b/list-objects-filter-options.h
@@ -10,6 +10,7 @@ enum list_objects_filter_choice {
 	LOFC_DISABLED = 0,
 	LOFC_BLOB_NONE,
 	LOFC_BLOB_LIMIT,
+	LOFC_TREE_NONE,
 	LOFC_SPARSE_OID,
 	LOFC_SPARSE_PATH,
 	LOFC__COUNT /* must be last */
diff --git a/list-objects-filter.c b/list-objects-filter.c
index a0ba78b20c..765f3df3b0 100644
--- a/list-objects-filter.c
+++ b/list-objects-filter.c
@@ -44,8 +44,7 @@ static enum list_objects_filter_result filter_blobs_none(
 
 	switch (filter_situation) {
 	default:
-		die("unknown filter_situation");
-		return LOFR_ZERO;
+		BUG("unknown filter_situation: %d", filter_situation);
 
 	case LOFS_BEGIN_TREE:
 		assert(obj->type == OBJ_TREE);
@@ -81,6 +80,61 @@ static void *filter_blobs_none__init(
 }
 
 /*
+ * A filter for list-objects to omit ALL trees and blobs from the traversal.
+ * Can OPTIONALLY collect a list of the omitted OIDs.
+ */
+struct filter_trees_none_data {
+	struct oidset *omits;
+};
+
+static enum list_objects_filter_result filter_trees_none(
+	enum list_objects_filter_situation filter_situation,
+	struct object *obj,
+	const char *pathname,
+	const char *filename,
+	void *filter_data_)
+{
+	struct filter_trees_none_data *filter_data = filter_data_;
+
+	switch (filter_situation) {
+	default:
+		BUG("unknown filter_situation: %d", filter_situation);
+
+	case LOFS_BEGIN_TREE:
+	case LOFS_BLOB:
+		if (filter_data->omits) {
+			oidset_insert(filter_data->omits, &obj->oid);
+			/* _MARK_SEEN but not _DO_SHOW (hard omit) */
+			return LOFR_MARK_SEEN;
+		} else {
+			/*
+			 * Not collecting omits so no need to to traverse tree.
+			 */
+			return LOFR_SKIP_TREE | LOFR_MARK_SEEN;
+		}
+
+	case LOFS_END_TREE:
+		assert(obj->type == OBJ_TREE);
+		return LOFR_ZERO;
+
+	}
+}
+
+static void* filter_trees_none__init(
+	struct oidset *omitted,
+	struct list_objects_filter_options *filter_options,
+	filter_object_fn *filter_fn,
+	filter_free_fn *filter_free_fn)
+{
+	struct filter_trees_none_data *d = xcalloc(1, sizeof(*d));
+	d->omits = omitted;
+
+	*filter_fn = filter_trees_none;
+	*filter_free_fn = free;
+	return d;
+}
+
+/*
  * A filter for list-objects to omit large blobs.
  * And to OPTIONALLY collect a list of the omitted OIDs.
  */
@@ -102,8 +156,7 @@ static enum list_objects_filter_result filter_blobs_limit(
 
 	switch (filter_situation) {
 	default:
-		die("unknown filter_situation");
-		return LOFR_ZERO;
+		BUG("unknown filter_situation: %d", filter_situation);
 
 	case LOFS_BEGIN_TREE:
 		assert(obj->type == OBJ_TREE);
@@ -208,8 +261,7 @@ static enum list_objects_filter_result filter_sparse(
 
 	switch (filter_situation) {
 	default:
-		die("unknown filter_situation");
-		return LOFR_ZERO;
+		BUG("unknown filter_situation: %d", filter_situation);
 
 	case LOFS_BEGIN_TREE:
 		assert(obj->type == OBJ_TREE);
@@ -374,6 +426,7 @@ static filter_init_fn s_filters[] = {
 	NULL,
 	filter_blobs_none__init,
 	filter_blobs_limit__init,
+	filter_trees_none__init,
 	filter_sparse_oid__init,
 	filter_sparse_path__init,
 };
@@ -389,7 +442,7 @@ void *list_objects_filter__init(
 	assert((sizeof(s_filters) / sizeof(s_filters[0])) == LOFC__COUNT);
 
 	if (filter_options->choice >= LOFC__COUNT)
-		die("invalid list-objects filter choice: %d",
+		BUG("invalid list-objects filter choice: %d",
 		    filter_options->choice);
 
 	init_fn = s_filters[filter_options->choice];
diff --git a/list-objects-filter.h b/list-objects-filter.h
index a6f6b4990b..52b4a84da9 100644
--- a/list-objects-filter.h
+++ b/list-objects-filter.h
@@ -24,6 +24,11 @@ struct oidset;
  *              In general, objects should only be shown once, but
  *              this result DOES NOT imply that we mark it SEEN.
  *
+ * _SKIP_TREE : Used in LOFS_BEGIN_TREE situation - indicates that
+ *              the tree's children should not be iterated over. This
+ *              is used as an optimization when all children will
+ *              definitely be ignored.
+ *
  * Most of the time, you want the combination (_MARK_SEEN | _DO_SHOW)
  * but they can be used independently, such as when sparse-checkout
  * pattern matching is being applied.
@@ -45,6 +50,7 @@ enum list_objects_filter_result {
 	LOFR_ZERO      = 0,
 	LOFR_MARK_SEEN = 1<<0,
 	LOFR_DO_SHOW   = 1<<1,
+	LOFR_SKIP_TREE = 1<<2,
 };
 
 enum list_objects_filter_situation {
diff --git a/list-objects.c b/list-objects.c
index 0c2989d5ca..c41cc80db5 100644
--- a/list-objects.c
+++ b/list-objects.c
@@ -11,21 +11,27 @@
 #include "list-objects-filter-options.h"
 #include "packfile.h"
 #include "object-store.h"
+#include "trace.h"
 
-static void process_blob(struct rev_info *revs,
+struct traversal_context {
+	struct rev_info *revs;
+	show_object_fn show_object;
+	show_commit_fn show_commit;
+	void *show_data;
+	filter_object_fn filter_fn;
+	void *filter_data;
+};
+
+static void process_blob(struct traversal_context *ctx,
 			 struct blob *blob,
-			 show_object_fn show,
 			 struct strbuf *path,
-			 const char *name,
-			 void *cb_data,
-			 filter_object_fn filter_fn,
-			 void *filter_data)
+			 const char *name)
 {
 	struct object *obj = &blob->object;
 	size_t pathlen;
 	enum list_objects_filter_result r = LOFR_MARK_SEEN | LOFR_DO_SHOW;
 
-	if (!revs->blob_objects)
+	if (!ctx->revs->blob_objects)
 		return;
 	if (!obj)
 		die("bad blob object");
@@ -41,21 +47,21 @@ static void process_blob(struct rev_info *revs,
 	 * may cause the actual filter to report an incomplete list
 	 * of missing objects.
 	 */
-	if (revs->exclude_promisor_objects &&
+	if (ctx->revs->exclude_promisor_objects &&
 	    !has_object_file(&obj->oid) &&
 	    is_promisor_object(&obj->oid))
 		return;
 
 	pathlen = path->len;
 	strbuf_addstr(path, name);
-	if (!(obj->flags & USER_GIVEN) && filter_fn)
-		r = filter_fn(LOFS_BLOB, obj,
-			      path->buf, &path->buf[pathlen],
-			      filter_data);
+	if ((obj->flags & NOT_USER_GIVEN) && ctx->filter_fn)
+		r = ctx->filter_fn(LOFS_BLOB, obj,
+				   path->buf, &path->buf[pathlen],
+				   ctx->filter_data);
 	if (r & LOFR_MARK_SEEN)
 		obj->flags |= SEEN;
 	if (r & LOFR_DO_SHOW)
-		show(obj, path->buf, cb_data);
+		ctx->show_object(obj, path->buf, ctx->show_data);
 	strbuf_setlen(path, pathlen);
 }
 
@@ -81,34 +87,66 @@ static void process_blob(struct rev_info *revs,
  * the link, and how to do it. Whether it necessarily makes
  * any sense what-so-ever to ever do that is another issue.
  */
-static void process_gitlink(struct rev_info *revs,
+static void process_gitlink(struct traversal_context *ctx,
 			    const unsigned char *sha1,
-			    show_object_fn show,
 			    struct strbuf *path,
-			    const char *name,
-			    void *cb_data)
+			    const char *name)
 {
 	/* Nothing to do */
 }
 
-static void process_tree(struct rev_info *revs,
+static void process_tree(struct traversal_context *ctx,
 			 struct tree *tree,
-			 show_object_fn show,
 			 struct strbuf *base,
-			 const char *name,
-			 void *cb_data,
-			 filter_object_fn filter_fn,
-			 void *filter_data)
+			 const char *name);
+
+static void process_tree_contents(struct traversal_context *ctx,
+				  struct tree *tree,
+				  struct strbuf *base)
 {
-	struct object *obj = &tree->object;
 	struct tree_desc desc;
 	struct name_entry entry;
-	enum interesting match = revs->diffopt.pathspec.nr == 0 ?
-		all_entries_interesting: entry_not_interesting;
+	enum interesting match = ctx->revs->diffopt.pathspec.nr == 0 ?
+		all_entries_interesting : entry_not_interesting;
+
+	init_tree_desc(&desc, tree->buffer, tree->size);
+
+	while (tree_entry(&desc, &entry)) {
+		if (match != all_entries_interesting) {
+			match = tree_entry_interesting(&entry, base, 0,
+						       &ctx->revs->diffopt.pathspec);
+			if (match == all_entries_not_interesting)
+				break;
+			if (match == entry_not_interesting)
+				continue;
+		}
+
+		if (S_ISDIR(entry.mode)) {
+			struct tree *t = lookup_tree(the_repository, entry.oid);
+			t->object.flags |= NOT_USER_GIVEN;
+			process_tree(ctx, t, base, entry.path);
+		}
+		else if (S_ISGITLINK(entry.mode))
+			process_gitlink(ctx, entry.oid->hash,
+					base, entry.path);
+		else {
+			struct blob *b = lookup_blob(the_repository, entry.oid);
+			b->object.flags |= NOT_USER_GIVEN;
+			process_blob(ctx, b, base, entry.path);
+		}
+	}
+}
+
+static void process_tree(struct traversal_context *ctx,
+			 struct tree *tree,
+			 struct strbuf *base,
+			 const char *name)
+{
+	struct object *obj = &tree->object;
+	struct rev_info *revs = ctx->revs;
 	int baselen = base->len;
 	enum list_objects_filter_result r = LOFR_MARK_SEEN | LOFR_DO_SHOW;
-	int gently = revs->ignore_missing_links ||
-		     revs->exclude_promisor_objects;
+	int failed_parse;
 
 	if (!revs->tree_objects)
 		return;
@@ -116,7 +154,9 @@ static void process_tree(struct rev_info *revs,
 		die("bad tree object");
 	if (obj->flags & (UNINTERESTING | SEEN))
 		return;
-	if (parse_tree_gently(tree, gently) < 0) {
+
+	failed_parse = parse_tree_gently(tree, 1);
+	if (failed_parse) {
 		if (revs->ignore_missing_links)
 			return;
 
@@ -129,57 +169,35 @@ static void process_tree(struct rev_info *revs,
 		    is_promisor_object(&obj->oid))
 			return;
 
-		die("bad tree object %s", oid_to_hex(&obj->oid));
+		if (!revs->do_not_die_on_missing_tree)
+			die("bad tree object %s", oid_to_hex(&obj->oid));
 	}
 
 	strbuf_addstr(base, name);
-	if (!(obj->flags & USER_GIVEN) && filter_fn)
-		r = filter_fn(LOFS_BEGIN_TREE, obj,
-			      base->buf, &base->buf[baselen],
-			      filter_data);
+	if ((obj->flags & NOT_USER_GIVEN) && ctx->filter_fn)
+		r = ctx->filter_fn(LOFS_BEGIN_TREE, obj,
+				   base->buf, &base->buf[baselen],
+				   ctx->filter_data);
 	if (r & LOFR_MARK_SEEN)
 		obj->flags |= SEEN;
 	if (r & LOFR_DO_SHOW)
-		show(obj, base->buf, cb_data);
+		ctx->show_object(obj, base->buf, ctx->show_data);
 	if (base->len)
 		strbuf_addch(base, '/');
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	if (r & LOFR_SKIP_TREE)
+		trace_printf("Skipping contents of tree %s...\n", base->buf);
+	else if (!failed_parse)
+		process_tree_contents(ctx, tree, base);
 
-	while (tree_entry(&desc, &entry)) {
-		if (match != all_entries_interesting) {
-			match = tree_entry_interesting(&entry, base, 0,
-						       &revs->diffopt.pathspec);
-			if (match == all_entries_not_interesting)
-				break;
-			if (match == entry_not_interesting)
-				continue;
-		}
-
-		if (S_ISDIR(entry.mode))
-			process_tree(revs,
-				     lookup_tree(the_repository, entry.oid),
-				     show, base, entry.path,
-				     cb_data, filter_fn, filter_data);
-		else if (S_ISGITLINK(entry.mode))
-			process_gitlink(revs, entry.oid->hash,
-					show, base, entry.path,
-					cb_data);
-		else
-			process_blob(revs,
-				     lookup_blob(the_repository, entry.oid),
-				     show, base, entry.path,
-				     cb_data, filter_fn, filter_data);
-	}
-
-	if (!(obj->flags & USER_GIVEN) && filter_fn) {
-		r = filter_fn(LOFS_END_TREE, obj,
-			      base->buf, &base->buf[baselen],
-			      filter_data);
+	if ((obj->flags & NOT_USER_GIVEN) && ctx->filter_fn) {
+		r = ctx->filter_fn(LOFS_END_TREE, obj,
+				   base->buf, &base->buf[baselen],
+				   ctx->filter_data);
 		if (r & LOFR_MARK_SEEN)
 			obj->flags |= SEEN;
 		if (r & LOFR_DO_SHOW)
-			show(obj, base->buf, cb_data);
+			ctx->show_object(obj, base->buf, ctx->show_data);
 	}
 
 	strbuf_setlen(base, baselen);
@@ -244,19 +262,15 @@ static void add_pending_tree(struct rev_info *revs, struct tree *tree)
 	add_pending_object(revs, &tree->object, "");
 }
 
-static void traverse_trees_and_blobs(struct rev_info *revs,
-				     struct strbuf *base,
-				     show_object_fn show_object,
-				     void *show_data,
-				     filter_object_fn filter_fn,
-				     void *filter_data)
+static void traverse_trees_and_blobs(struct traversal_context *ctx,
+				     struct strbuf *base)
 {
 	int i;
 
 	assert(base->len == 0);
 
-	for (i = 0; i < revs->pending.nr; i++) {
-		struct object_array_entry *pending = revs->pending.objects + i;
+	for (i = 0; i < ctx->revs->pending.nr; i++) {
+		struct object_array_entry *pending = ctx->revs->pending.objects + i;
 		struct object *obj = pending->item;
 		const char *name = pending->name;
 		const char *path = pending->path;
@@ -264,62 +278,52 @@ static void traverse_trees_and_blobs(struct rev_info *revs,
 			continue;
 		if (obj->type == OBJ_TAG) {
 			obj->flags |= SEEN;
-			show_object(obj, name, show_data);
+			ctx->show_object(obj, name, ctx->show_data);
 			continue;
 		}
 		if (!path)
 			path = "";
 		if (obj->type == OBJ_TREE) {
-			process_tree(revs, (struct tree *)obj, show_object,
-				     base, path, show_data,
-				     filter_fn, filter_data);
+			process_tree(ctx, (struct tree *)obj, base, path);
 			continue;
 		}
 		if (obj->type == OBJ_BLOB) {
-			process_blob(revs, (struct blob *)obj, show_object,
-				     base, path, show_data,
-				     filter_fn, filter_data);
+			process_blob(ctx, (struct blob *)obj, base, path);
 			continue;
 		}
 		die("unknown pending object %s (%s)",
 		    oid_to_hex(&obj->oid), name);
 	}
-	object_array_clear(&revs->pending);
+	object_array_clear(&ctx->revs->pending);
 }
 
-static void do_traverse(struct rev_info *revs,
-			show_commit_fn show_commit,
-			show_object_fn show_object,
-			void *show_data,
-			filter_object_fn filter_fn,
-			void *filter_data)
+static void do_traverse(struct traversal_context *ctx)
 {
 	struct commit *commit;
 	struct strbuf csp; /* callee's scratch pad */
 	strbuf_init(&csp, PATH_MAX);
 
-	while ((commit = get_revision(revs)) != NULL) {
+	while ((commit = get_revision(ctx->revs)) != NULL) {
 		/*
 		 * an uninteresting boundary commit may not have its tree
 		 * parsed yet, but we are not going to show them anyway
 		 */
-		if (get_commit_tree(commit))
-			add_pending_tree(revs, get_commit_tree(commit));
-		show_commit(commit, show_data);
+		if (get_commit_tree(commit)) {
+			struct tree *tree = get_commit_tree(commit);
+			tree->object.flags |= NOT_USER_GIVEN;
+			add_pending_tree(ctx->revs, tree);
+		}
+		ctx->show_commit(commit, ctx->show_data);
 
-		if (revs->tree_blobs_in_commit_order)
+		if (ctx->revs->tree_blobs_in_commit_order)
 			/*
 			 * NEEDSWORK: Adding the tree and then flushing it here
 			 * needs a reallocation for each commit. Can we pass the
 			 * tree directory without allocation churn?
 			 */
-			traverse_trees_and_blobs(revs, &csp,
-						 show_object, show_data,
-						 filter_fn, filter_data);
+			traverse_trees_and_blobs(ctx, &csp);
 	}
-	traverse_trees_and_blobs(revs, &csp,
-				 show_object, show_data,
-				 filter_fn, filter_data);
+	traverse_trees_and_blobs(ctx, &csp);
 	strbuf_release(&csp);
 }
 
@@ -328,7 +332,14 @@ void traverse_commit_list(struct rev_info *revs,
 			  show_object_fn show_object,
 			  void *show_data)
 {
-	do_traverse(revs, show_commit, show_object, show_data, NULL, NULL);
+	struct traversal_context ctx;
+	ctx.revs = revs;
+	ctx.show_commit = show_commit;
+	ctx.show_object = show_object;
+	ctx.show_data = show_data;
+	ctx.filter_fn = NULL;
+	ctx.filter_data = NULL;
+	do_traverse(&ctx);
 }
 
 void traverse_commit_list_filtered(
@@ -339,14 +350,18 @@ void traverse_commit_list_filtered(
 	void *show_data,
 	struct oidset *omitted)
 {
-	filter_object_fn filter_fn = NULL;
+	struct traversal_context ctx;
 	filter_free_fn filter_free_fn = NULL;
-	void *filter_data = NULL;
-
-	filter_data = list_objects_filter__init(omitted, filter_options,
-						&filter_fn, &filter_free_fn);
-	do_traverse(revs, show_commit, show_object, show_data,
-		    filter_fn, filter_data);
-	if (filter_data && filter_free_fn)
-		filter_free_fn(filter_data);
+
+	ctx.revs = revs;
+	ctx.show_object = show_object;
+	ctx.show_commit = show_commit;
+	ctx.show_data = show_data;
+	ctx.filter_fn = NULL;
+
+	ctx.filter_data = list_objects_filter__init(omitted, filter_options,
+						    &ctx.filter_fn, &filter_free_fn);
+	do_traverse(&ctx);
+	if (ctx.filter_data && filter_free_fn)
+		filter_free_fn(ctx.filter_data);
 }
diff --git a/revision.c b/revision.c
index b5108b75ab..a1ddb9e11c 100644
--- a/revision.c
+++ b/revision.c
@@ -177,7 +177,6 @@ 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);
 }
 
diff --git a/revision.h b/revision.h
index bc30a3023e..1cd0c4b200 100644
--- a/revision.h
+++ b/revision.h
@@ -21,9 +21,16 @@
 #define SYMMETRIC_LEFT	(1u<<8)
 #define PATCHSAME	(1u<<9)
 #define BOTTOM		(1u<<10)
-#define USER_GIVEN	(1u<<25) /* given directly by the user */
+/*
+ * Indicates object was reached by traversal. i.e. not given by user on
+ * command-line or stdin.
+ * NEEDSWORK: NOT_USER_GIVEN doesn't apply to commits because we only support
+ * filtering trees and blobs, but it may be useful to support filtering commits
+ * in the future.
+ */
+#define NOT_USER_GIVEN	(1u<<25)
 #define TRACK_LINEAR	(1u<<26)
-#define ALL_REV_FLAGS	(((1u<<11)-1) | USER_GIVEN | TRACK_LINEAR)
+#define ALL_REV_FLAGS	(((1u<<11)-1) | NOT_USER_GIVEN | TRACK_LINEAR)
 
 #define DECORATE_SHORT_REFS	1
 #define DECORATE_FULL_REFS	2
@@ -133,6 +140,21 @@ struct rev_info {
 			line_level_traverse:1,
 			tree_blobs_in_commit_order:1,
 
+			/*
+			 * Blobs are shown without regard for their existence.
+			 * But not so for trees: unless exclude_promisor_objects
+			 * is set and the tree in question is a promisor object;
+			 * OR ignore_missing_links is set, the revision walker
+			 * dies with a "bad tree object HASH" message when
+			 * encountering a missing tree. For callers that can
+			 * handle missing trees and want them to be filterable
+			 * and showable, set this to true. The revision walker
+			 * will filter and show such a missing tree as usual,
+			 * but will not attempt to recurse into this tree
+			 * object.
+			 */
+			do_not_die_on_missing_tree:1,
+
 			/* for internal use only */
 			exclude_promisor_objects:1;
 
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index c521d7d6c6..ba3887f178 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -239,6 +239,51 @@ test_expect_success 'rev-list stops traversal at missing and promised commit' '
 	! grep $FOO out
 '
 
+test_expect_success 'missing tree objects with --missing=allow-promisor and --exclude-promisor-objects' '
+	rm -rf repo &&
+	test_create_repo repo &&
+	test_commit -C repo foo &&
+	test_commit -C repo bar &&
+	test_commit -C repo baz &&
+
+	promise_and_delete $(git -C repo rev-parse bar^{tree}) &&
+	promise_and_delete $(git -C repo rev-parse foo^{tree}) &&
+
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "arbitrary string" &&
+
+	git -C repo rev-list --missing=allow-promisor --objects HEAD >objs 2>rev_list_err &&
+	test_must_be_empty rev_list_err &&
+	# 3 commits, 3 blobs, and 1 tree
+	test_line_count = 7 objs &&
+
+	# Do the same for --exclude-promisor-objects, but with all trees gone.
+	promise_and_delete $(git -C repo rev-parse baz^{tree}) &&
+	git -C repo rev-list --exclude-promisor-objects --objects HEAD >objs 2>rev_list_err &&
+	test_must_be_empty rev_list_err &&
+	# 3 commits, no blobs or trees
+	test_line_count = 3 objs
+'
+
+test_expect_success 'missing non-root tree object and rev-list' '
+	rm -rf repo &&
+	test_create_repo repo &&
+	mkdir repo/dir &&
+	echo foo >repo/dir/foo &&
+	git -C repo add dir/foo &&
+	git -C repo commit -m "commit dir/foo" &&
+
+	promise_and_delete $(git -C repo rev-parse HEAD:dir) &&
+
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "arbitrary string" &&
+
+	git -C repo rev-list --missing=allow-any --objects HEAD >objs 2>rev_list_err &&
+	test_must_be_empty rev_list_err &&
+	# 1 commit and 1 tree
+	test_line_count = 2 objs
+'
+
 test_expect_success 'rev-list stops traversal at missing and promised tree' '
 	rm -rf repo &&
 	test_create_repo repo &&
diff --git a/t/t5317-pack-objects-filter-objects.sh b/t/t5317-pack-objects-filter-objects.sh
index 2e718f0bde..24541ea137 100755
--- a/t/t5317-pack-objects-filter-objects.sh
+++ b/t/t5317-pack-objects-filter-objects.sh
@@ -67,6 +67,47 @@ test_expect_success 'verify normal and blob:none packfiles have same commits/tre
 	test_cmp expected observed
 '
 
+test_expect_success 'get an error for missing tree object' '
+	git init r5 &&
+	echo foo >r5/foo &&
+	git -C r5 add foo &&
+	git -C r5 commit -m "foo" &&
+	del=$(git -C r5 rev-parse HEAD^{tree} | sed "s|..|&/|") &&
+	rm r5/.git/objects/$del &&
+	test_must_fail git -C r5 pack-objects --rev --stdout 2>bad_tree <<-EOF &&
+	HEAD
+	EOF
+	grep "bad tree object" bad_tree
+'
+
+test_expect_success 'setup for tests of tree:0' '
+	mkdir r1/subtree &&
+	echo "This is a file in a subtree" >r1/subtree/file &&
+	git -C r1 add subtree/file &&
+	git -C r1 commit -m subtree
+'
+
+test_expect_success 'verify tree:0 packfile has no blobs or trees' '
+	git -C r1 pack-objects --rev --stdout --filter=tree:0 >commitsonly.pack <<-EOF &&
+	HEAD
+	EOF
+	git -C r1 index-pack ../commitsonly.pack &&
+	git -C r1 verify-pack -v ../commitsonly.pack >objs &&
+	! grep -E "tree|blob" objs
+'
+
+test_expect_success 'grab tree directly when using tree:0' '
+	# We should get the tree specified directly but not its blobs or subtrees.
+	git -C r1 pack-objects --rev --stdout --filter=tree:0 >commitsonly.pack <<-EOF &&
+	HEAD:
+	EOF
+	git -C r1 index-pack ../commitsonly.pack &&
+	git -C r1 verify-pack -v ../commitsonly.pack >objs &&
+	awk "/tree|blob/{print \$1}" objs >trees_and_blobs &&
+	git -C r1 rev-parse HEAD: >expected &&
+	test_cmp expected trees_and_blobs
+'
+
 # Test blob:limit=<n>[kmg] filter.
 # We boundary test around the size parameter.  The filter is strictly less than
 # the value, so size 500 and 1000 should have the same results, but 1001 should
diff --git a/t/t5616-partial-clone.sh b/t/t5616-partial-clone.sh
index 6391437529..336f02a41a 100755
--- a/t/t5616-partial-clone.sh
+++ b/t/t5616-partial-clone.sh
@@ -166,6 +166,48 @@ test_expect_success 'partial clone with transfer.fsckobjects=1 uses index-pack -
 	grep "git index-pack.*--fsck-objects" trace
 '
 
+test_expect_success 'use fsck before and after manually fetching a missing subtree' '
+	# push new commit so server has a subtree
+	mkdir src/dir &&
+	echo "in dir" >src/dir/file.txt &&
+	git -C src add dir/file.txt &&
+	git -C src commit -m "file in dir" &&
+	git -C src push -u srv master &&
+	SUBTREE=$(git -C src rev-parse HEAD:dir) &&
+
+	rm -rf dst &&
+	git clone --no-checkout --filter=tree:0 "file://$(pwd)/srv.bare" dst &&
+	git -C dst fsck &&
+
+	# Make sure we only have commits, and all trees and blobs are missing.
+	git -C dst rev-list --missing=allow-any --objects master \
+		>fetched_objects &&
+	awk -f print_1.awk fetched_objects |
+	xargs -n1 git -C dst cat-file -t >fetched_types &&
+
+	sort -u fetched_types >unique_types.observed &&
+	echo commit >unique_types.expected &&
+	test_cmp unique_types.expected unique_types.observed &&
+
+	# Auto-fetch a tree with cat-file.
+	git -C dst cat-file -p $SUBTREE >tree_contents &&
+	grep file.txt tree_contents &&
+
+	# fsck still works after an auto-fetch of a tree.
+	git -C dst fsck &&
+
+	# Auto-fetch all remaining trees and blobs with --missing=error
+	git -C dst rev-list --missing=error --objects master >fetched_objects &&
+	test_line_count = 70 fetched_objects &&
+
+	awk -f print_1.awk fetched_objects |
+	xargs -n1 git -C dst cat-file -t >fetched_types &&
+
+	sort -u fetched_types >unique_types.observed &&
+	test_write_lines blob commit tree >unique_types.expected &&
+	test_cmp unique_types.expected unique_types.observed
+'
+
 test_expect_success 'partial clone fetches blobs pointed to by refs even if normally filtered out' '
 	rm -rf src dst &&
 	git init src &&
diff --git a/t/t6112-rev-list-filters-objects.sh b/t/t6112-rev-list-filters-objects.sh
index 53975c5724..eb32505a6e 100755
--- a/t/t6112-rev-list-filters-objects.sh
+++ b/t/t6112-rev-list-filters-objects.sh
@@ -34,6 +34,18 @@ test_expect_success 'verify blob:none omits all 5 blobs' '
 	test_cmp expected observed
 '
 
+test_expect_success 'specify blob explicitly prevents filtering' '
+	file_3=$(git -C r1 ls-files -s file.3 |
+		 awk -f print_2.awk) &&
+
+	file_4=$(git -C r1 ls-files -s file.4 |
+		 awk -f print_2.awk) &&
+
+	git -C r1 rev-list --objects --filter=blob:none HEAD $file_3 >observed &&
+	grep "$file_3" observed &&
+	! grep "$file_4" observed
+'
+
 test_expect_success 'verify emitted+omitted == all' '
 	git -C r1 rev-list --objects HEAD >revs &&
 	awk -f print_1.awk revs |
@@ -232,6 +244,56 @@ test_expect_success 'verify sparse:oid=oid-ish omits top-level files' '
 	test_cmp expected observed
 '
 
+test_expect_success 'rev-list W/ --missing=print and --missing=allow-any for trees' '
+	TREE=$(git -C r3 rev-parse HEAD:dir1) &&
+
+	# Create a spare repo because we will be deleting objects from this one.
+	git clone r3 r3.b &&
+
+	rm r3.b/.git/objects/$(echo $TREE | sed "s|^..|&/|") &&
+
+	git -C r3.b rev-list --quiet --missing=print --objects HEAD \
+		>missing_objs 2>rev_list_err &&
+	echo "?$TREE" >expected &&
+	test_cmp expected missing_objs &&
+
+	# do not complain when a missing tree cannot be parsed
+	test_must_be_empty rev_list_err &&
+
+	git -C r3.b rev-list --missing=allow-any --objects HEAD \
+		>objs 2>rev_list_err &&
+	! grep $TREE objs &&
+	test_must_be_empty rev_list_err
+'
+
+# Test tree:0 filter.
+
+test_expect_success 'verify tree:0 includes trees in "filtered" output' '
+	git -C r3 rev-list --quiet --objects --filter-print-omitted \
+		--filter=tree:0 HEAD >revs &&
+
+	awk -f print_1.awk revs |
+	sed s/~// |
+	xargs -n1 git -C r3 cat-file -t >unsorted_filtered_types &&
+
+	sort -u unsorted_filtered_types >filtered_types &&
+	test_write_lines blob tree >expected &&
+	test_cmp expected filtered_types
+'
+
+# Make sure tree:0 does not iterate through any trees.
+
+test_expect_success 'filter a GIANT tree through tree:0' '
+	GIT_TRACE=1 git -C r3 rev-list \
+		--objects --filter=tree:0 HEAD 2>filter_trace &&
+	grep "Skipping contents of tree [.][.][.]" filter_trace >actual &&
+	# One line for each commit traversed.
+	test_line_count = 2 actual &&
+
+	# Make sure no other trees were considered besides the root.
+	! grep "Skipping contents of tree [^.]" filter_trace
+'
+
 # Delete some loose objects and use rev-list, but WITHOUT any filtering.
 # This models previously omitted objects that we did not receive.