merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 409 insertions, 213 deletions

diff --git a/third_party/git/fsck.c b/third_party/git/fsck.c
index cdb7d8db03..f82e2fe9e3 100644
--- a/third_party/git/fsck.c
+++ b/third_party/git/fsck.c
@@ -9,12 +9,14 @@
 #include "tag.h"
 #include "fsck.h"
 #include "refs.h"
+#include "url.h"
 #include "utf8.h"
 #include "decorate.h"
 #include "oidset.h"
 #include "packfile.h"
 #include "submodule-config.h"
 #include "config.h"
+#include "credential.h"
 #include "help.h"
 
 static struct oidset gitmodules_found = OIDSET_INIT;
@@ -43,21 +45,17 @@ static struct oidset gitmodules_done = OIDSET_INIT;
 	FUNC(MISSING_AUTHOR, ERROR) \
 	FUNC(MISSING_COMMITTER, ERROR) \
 	FUNC(MISSING_EMAIL, ERROR) \
-	FUNC(MISSING_GRAFT, ERROR) \
 	FUNC(MISSING_NAME_BEFORE_EMAIL, ERROR) \
 	FUNC(MISSING_OBJECT, ERROR) \
-	FUNC(MISSING_PARENT, ERROR) \
 	FUNC(MISSING_SPACE_BEFORE_DATE, ERROR) \
 	FUNC(MISSING_SPACE_BEFORE_EMAIL, ERROR) \
 	FUNC(MISSING_TAG, ERROR) \
 	FUNC(MISSING_TAG_ENTRY, ERROR) \
-	FUNC(MISSING_TAG_OBJECT, ERROR) \
 	FUNC(MISSING_TREE, ERROR) \
 	FUNC(MISSING_TREE_OBJECT, ERROR) \
 	FUNC(MISSING_TYPE, ERROR) \
 	FUNC(MISSING_TYPE_ENTRY, ERROR) \
 	FUNC(MULTIPLE_AUTHORS, ERROR) \
-	FUNC(TAG_OBJECT_NOT_TAG, ERROR) \
 	FUNC(TREE_NOT_SORTED, ERROR) \
 	FUNC(UNKNOWN_TYPE, ERROR) \
 	FUNC(ZERO_PADDED_DATE, ERROR) \
@@ -68,6 +66,7 @@ static struct oidset gitmodules_done = OIDSET_INIT;
 	FUNC(GITMODULES_SYMLINK, ERROR) \
 	FUNC(GITMODULES_URL, ERROR) \
 	FUNC(GITMODULES_PATH, ERROR) \
+	FUNC(GITMODULES_UPDATE, ERROR) \
 	/* warnings */ \
 	FUNC(BAD_FILEMODE, WARN) \
 	FUNC(EMPTY_NAME, WARN) \
@@ -281,14 +280,16 @@ static void append_msg_id(struct strbuf *sb, const char *msg_id)
 	strbuf_addstr(sb, ": ");
 }
 
-static int object_on_skiplist(struct fsck_options *opts, struct object *obj)
+static int object_on_skiplist(struct fsck_options *opts,
+			      const struct object_id *oid)
 {
-	return opts && obj && oidset_contains(&opts->skiplist, &obj->oid);
+	return opts && oid && oidset_contains(&opts->skiplist, oid);
 }
 
-__attribute__((format (printf, 4, 5)))
-static int report(struct fsck_options *options, struct object *object,
-	enum fsck_msg_id id, const char *fmt, ...)
+__attribute__((format (printf, 5, 6)))
+static int report(struct fsck_options *options,
+		  const struct object_id *oid, enum object_type object_type,
+		  enum fsck_msg_id id, const char *fmt, ...)
 {
 	va_list ap;
 	struct strbuf sb = STRBUF_INIT;
@@ -297,7 +298,7 @@ static int report(struct fsck_options *options, struct object *object,
 	if (msg_type == FSCK_IGNORE)
 		return 0;
 
-	if (object_on_skiplist(options, object))
+	if (object_on_skiplist(options, oid))
 		return 0;
 
 	if (msg_type == FSCK_FATAL)
@@ -309,49 +310,71 @@ static int report(struct fsck_options *options, struct object *object,
 
 	va_start(ap, fmt);
 	strbuf_vaddf(&sb, fmt, ap);
-	result = options->error_func(options, object, msg_type, sb.buf);
+	result = options->error_func(options, oid, object_type,
+				     msg_type, sb.buf);
 	strbuf_release(&sb);
 	va_end(ap);
 
 	return result;
 }
 
-static char *get_object_name(struct fsck_options *options, struct object *obj)
+void fsck_enable_object_names(struct fsck_options *options)
 {
 	if (!options->object_names)
+		options->object_names = kh_init_oid_map();
+}
+
+const char *fsck_get_object_name(struct fsck_options *options,
+				 const struct object_id *oid)
+{
+	khiter_t pos;
+	if (!options->object_names)
 		return NULL;
-	return lookup_decoration(options->object_names, obj);
+	pos = kh_get_oid_map(options->object_names, *oid);
+	if (pos >= kh_end(options->object_names))
+		return NULL;
+	return kh_value(options->object_names, pos);
 }
 
-static void put_object_name(struct fsck_options *options, struct object *obj,
-	const char *fmt, ...)
+void fsck_put_object_name(struct fsck_options *options,
+			  const struct object_id *oid,
+			  const char *fmt, ...)
 {
 	va_list ap;
 	struct strbuf buf = STRBUF_INIT;
-	char *existing;
+	khiter_t pos;
+	int hashret;
 
 	if (!options->object_names)
 		return;
-	existing = lookup_decoration(options->object_names, obj);
-	if (existing)
+
+	pos = kh_put_oid_map(options->object_names, *oid, &hashret);
+	if (!hashret)
 		return;
 	va_start(ap, fmt);
 	strbuf_vaddf(&buf, fmt, ap);
-	add_decoration(options->object_names, obj, strbuf_detach(&buf, NULL));
+	kh_value(options->object_names, pos) = strbuf_detach(&buf, NULL);
 	va_end(ap);
 }
 
-static const char *describe_object(struct fsck_options *o, struct object *obj)
+const char *fsck_describe_object(struct fsck_options *options,
+				 const struct object_id *oid)
 {
-	static struct strbuf buf = STRBUF_INIT;
-	char *name;
-
-	strbuf_reset(&buf);
-	strbuf_addstr(&buf, oid_to_hex(&obj->oid));
-	if (o->object_names && (name = lookup_decoration(o->object_names, obj)))
-		strbuf_addf(&buf, " (%s)", name);
+	static struct strbuf bufs[] = {
+		STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
+	static int b = 0;
+	struct strbuf *buf;
+	const char *name = fsck_get_object_name(options, oid);
+
+	buf = bufs + b;
+	b = (b + 1) % ARRAY_SIZE(bufs);
+	strbuf_reset(buf);
+	strbuf_addstr(buf, oid_to_hex(oid));
+	if (name)
+		strbuf_addf(buf, " (%s)", name);
 
-	return buf.buf;
+	return buf->buf;
 }
 
 static int fsck_walk_tree(struct tree *tree, void *data, struct fsck_options *options)
@@ -364,7 +387,7 @@ static int fsck_walk_tree(struct tree *tree, void *data, struct fsck_options *op
 	if (parse_tree(tree))
 		return -1;
 
-	name = get_object_name(options, &tree->object);
+	name = fsck_get_object_name(options, &tree->object.oid);
 	if (init_tree_desc_gently(&desc, tree->buffer, tree->size))
 		return -1;
 	while (tree_entry_gently(&desc, &entry)) {
@@ -377,20 +400,21 @@ static int fsck_walk_tree(struct tree *tree, void *data, struct fsck_options *op
 		if (S_ISDIR(entry.mode)) {
 			obj = (struct object *)lookup_tree(the_repository, &entry.oid);
 			if (name && obj)
-				put_object_name(options, obj, "%s%s/", name,
-					entry.path);
+				fsck_put_object_name(options, &entry.oid, "%s%s/",
+						     name, entry.path);
 			result = options->walk(obj, OBJ_TREE, data, options);
 		}
 		else if (S_ISREG(entry.mode) || S_ISLNK(entry.mode)) {
 			obj = (struct object *)lookup_blob(the_repository, &entry.oid);
 			if (name && obj)
-				put_object_name(options, obj, "%s%s", name,
-					entry.path);
+				fsck_put_object_name(options, &entry.oid, "%s%s",
+						     name, entry.path);
 			result = options->walk(obj, OBJ_BLOB, data, options);
 		}
 		else {
 			result = error("in tree %s: entry %s has bad mode %.6o",
-					describe_object(options, &tree->object), entry.path, entry.mode);
+				       fsck_describe_object(options, &tree->object.oid),
+				       entry.path, entry.mode);
 		}
 		if (result < 0)
 			return result;
@@ -411,10 +435,10 @@ static int fsck_walk_commit(struct commit *commit, void *data, struct fsck_optio
 	if (parse_commit(commit))
 		return -1;
 
-	name = get_object_name(options, &commit->object);
+	name = fsck_get_object_name(options, &commit->object.oid);
 	if (name)
-		put_object_name(options, &get_commit_tree(commit)->object,
-				"%s:", name);
+		fsck_put_object_name(options, get_commit_tree_oid(commit),
+				     "%s:", name);
 
 	result = options->walk((struct object *)get_commit_tree(commit),
 			       OBJ_TREE, data, options);
@@ -442,16 +466,17 @@ static int fsck_walk_commit(struct commit *commit, void *data, struct fsck_optio
 
 	while (parents) {
 		if (name) {
-			struct object *obj = &parents->item->object;
+			struct object_id *oid = &parents->item->object.oid;
 
 			if (counter++)
-				put_object_name(options, obj, "%s^%d",
-					name, counter);
+				fsck_put_object_name(options, oid, "%s^%d",
+						     name, counter);
 			else if (generation > 0)
-				put_object_name(options, obj, "%.*s~%d",
-					name_prefix_len, name, generation + 1);
+				fsck_put_object_name(options, oid, "%.*s~%d",
+						     name_prefix_len, name,
+						     generation + 1);
 			else
-				put_object_name(options, obj, "%s^", name);
+				fsck_put_object_name(options, oid, "%s^", name);
 		}
 		result = options->walk((struct object *)parents->item, OBJ_COMMIT, data, options);
 		if (result < 0)
@@ -465,12 +490,12 @@ static int fsck_walk_commit(struct commit *commit, void *data, struct fsck_optio
 
 static int fsck_walk_tag(struct tag *tag, void *data, struct fsck_options *options)
 {
-	char *name = get_object_name(options, &tag->object);
+	const char *name = fsck_get_object_name(options, &tag->object.oid);
 
 	if (parse_tag(tag))
 		return -1;
 	if (name)
-		put_object_name(options, tag->tagged, "%s", name);
+		fsck_put_object_name(options, &tag->tagged->oid, "%s", name);
 	return options->walk(tag->tagged, OBJ_ANY, data, options);
 }
 
@@ -492,11 +517,34 @@ int fsck_walk(struct object *obj, void *data, struct fsck_options *options)
 	case OBJ_TAG:
 		return fsck_walk_tag((struct tag *)obj, data, options);
 	default:
-		error("Unknown object type for %s", describe_object(options, obj));
+		error("Unknown object type for %s",
+		      fsck_describe_object(options, &obj->oid));
 		return -1;
 	}
 }
 
+struct name_stack {
+	const char **names;
+	size_t nr, alloc;
+};
+
+static void name_stack_push(struct name_stack *stack, const char *name)
+{
+	ALLOC_GROW(stack->names, stack->nr + 1, stack->alloc);
+	stack->names[stack->nr++] = name;
+}
+
+static const char *name_stack_pop(struct name_stack *stack)
+{
+	return stack->nr ? stack->names[--stack->nr] : NULL;
+}
+
+static void name_stack_clear(struct name_stack *stack)
+{
+	FREE_AND_NULL(stack->names);
+	stack->nr = stack->alloc = 0;
+}
+
 /*
  * The entries in a tree are ordered in the _path_ order,
  * which means that a directory entry is ordered by adding
@@ -508,7 +556,14 @@ int fsck_walk(struct object *obj, void *data, struct fsck_options *options)
 #define TREE_UNORDERED (-1)
 #define TREE_HAS_DUPS  (-2)
 
-static int verify_ordered(unsigned mode1, const char *name1, unsigned mode2, const char *name2)
+static int is_less_than_slash(unsigned char c)
+{
+	return '\0' < c && c < '/';
+}
+
+static int verify_ordered(unsigned mode1, const char *name1,
+			  unsigned mode2, const char *name2,
+			  struct name_stack *candidates)
 {
 	int len1 = strlen(name1);
 	int len2 = strlen(name2);
@@ -540,10 +595,47 @@ static int verify_ordered(unsigned mode1, const char *name1, unsigned mode2, con
 		c1 = '/';
 	if (!c2 && S_ISDIR(mode2))
 		c2 = '/';
+
+	/*
+	 * There can be non-consecutive duplicates due to the implicitly
+	 * added slash, e.g.:
+	 *
+	 *   foo
+	 *   foo.bar
+	 *   foo.bar.baz
+	 *   foo.bar/
+	 *   foo/
+	 *
+	 * Record non-directory candidates (like "foo" and "foo.bar" in
+	 * the example) on a stack and check directory candidates (like
+	 * foo/" and "foo.bar/") against that stack.
+	 */
+	if (!c1 && is_less_than_slash(c2)) {
+		name_stack_push(candidates, name1);
+	} else if (c2 == '/' && is_less_than_slash(c1)) {
+		for (;;) {
+			const char *p;
+			const char *f_name = name_stack_pop(candidates);
+
+			if (!f_name)
+				break;
+			if (!skip_prefix(name2, f_name, &p))
+				continue;
+			if (!*p)
+				return TREE_HAS_DUPS;
+			if (is_less_than_slash(*p)) {
+				name_stack_push(candidates, f_name);
+				break;
+			}
+		}
+	}
+
 	return c1 < c2 ? 0 : TREE_UNORDERED;
 }
 
-static int fsck_tree(struct tree *item, struct fsck_options *options)
+static int fsck_tree(const struct object_id *oid,
+		     const char *buffer, unsigned long size,
+		     struct fsck_options *options)
 {
 	int retval = 0;
 	int has_null_sha1 = 0;
@@ -559,9 +651,10 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 	struct tree_desc desc;
 	unsigned o_mode;
 	const char *o_name;
+	struct name_stack df_dup_candidates = { NULL };
 
-	if (init_tree_desc_gently(&desc, item->buffer, item->size)) {
-		retval += report(options, &item->object, FSCK_MSG_BAD_TREE, "cannot be parsed as a tree");
+	if (init_tree_desc_gently(&desc, buffer, size)) {
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_BAD_TREE, "cannot be parsed as a tree");
 		return retval;
 	}
 
@@ -570,7 +663,7 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 
 	while (desc.size) {
 		unsigned short mode;
-		const char *name;
+		const char *name, *backslash;
 		const struct object_id *oid;
 
 		oid = tree_entry_extract(&desc, &name, &mode);
@@ -587,13 +680,30 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 			if (!S_ISLNK(mode))
 				oidset_insert(&gitmodules_found, oid);
 			else
-				retval += report(options, &item->object,
+				retval += report(options,
+						 oid, OBJ_TREE,
 						 FSCK_MSG_GITMODULES_SYMLINK,
 						 ".gitmodules is a symbolic link");
 		}
 
+		if ((backslash = strchr(name, '\\'))) {
+			while (backslash) {
+				backslash++;
+				has_dotgit |= is_ntfs_dotgit(backslash);
+				if (is_ntfs_dotgitmodules(backslash)) {
+					if (!S_ISLNK(mode))
+						oidset_insert(&gitmodules_found, oid);
+					else
+						retval += report(options, oid, OBJ_TREE,
+								 FSCK_MSG_GITMODULES_SYMLINK,
+								 ".gitmodules is a symbolic link");
+				}
+				backslash = strchr(backslash, '\\');
+			}
+		}
+
 		if (update_tree_entry_gently(&desc)) {
-			retval += report(options, &item->object, FSCK_MSG_BAD_TREE, "cannot be parsed as a tree");
+			retval += report(options, oid, OBJ_TREE, FSCK_MSG_BAD_TREE, "cannot be parsed as a tree");
 			break;
 		}
 
@@ -621,7 +731,8 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 		}
 
 		if (o_name) {
-			switch (verify_ordered(o_mode, o_name, mode, name)) {
+			switch (verify_ordered(o_mode, o_name, mode, name,
+					       &df_dup_candidates)) {
 			case TREE_UNORDERED:
 				not_properly_sorted = 1;
 				break;
@@ -637,31 +748,34 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 		o_name = name;
 	}
 
+	name_stack_clear(&df_dup_candidates);
+
 	if (has_null_sha1)
-		retval += report(options, &item->object, FSCK_MSG_NULL_SHA1, "contains entries pointing to null sha1");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_NULL_SHA1, "contains entries pointing to null sha1");
 	if (has_full_path)
-		retval += report(options, &item->object, FSCK_MSG_FULL_PATHNAME, "contains full pathnames");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_FULL_PATHNAME, "contains full pathnames");
 	if (has_empty_name)
-		retval += report(options, &item->object, FSCK_MSG_EMPTY_NAME, "contains empty pathname");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_EMPTY_NAME, "contains empty pathname");
 	if (has_dot)
-		retval += report(options, &item->object, FSCK_MSG_HAS_DOT, "contains '.'");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_HAS_DOT, "contains '.'");
 	if (has_dotdot)
-		retval += report(options, &item->object, FSCK_MSG_HAS_DOTDOT, "contains '..'");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_HAS_DOTDOT, "contains '..'");
 	if (has_dotgit)
-		retval += report(options, &item->object, FSCK_MSG_HAS_DOTGIT, "contains '.git'");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_HAS_DOTGIT, "contains '.git'");
 	if (has_zero_pad)
-		retval += report(options, &item->object, FSCK_MSG_ZERO_PADDED_FILEMODE, "contains zero-padded file modes");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_ZERO_PADDED_FILEMODE, "contains zero-padded file modes");
 	if (has_bad_modes)
-		retval += report(options, &item->object, FSCK_MSG_BAD_FILEMODE, "contains bad file modes");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_BAD_FILEMODE, "contains bad file modes");
 	if (has_dup_entries)
-		retval += report(options, &item->object, FSCK_MSG_DUPLICATE_ENTRIES, "contains duplicate file entries");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_DUPLICATE_ENTRIES, "contains duplicate file entries");
 	if (not_properly_sorted)
-		retval += report(options, &item->object, FSCK_MSG_TREE_NOT_SORTED, "not properly sorted");
+		retval += report(options, oid, OBJ_TREE, FSCK_MSG_TREE_NOT_SORTED, "not properly sorted");
 	return retval;
 }
 
 static int verify_headers(const void *data, unsigned long size,
-			  struct object *obj, struct fsck_options *options)
+			  const struct object_id *oid, enum object_type type,
+			  struct fsck_options *options)
 {
 	const char *buffer = (const char *)data;
 	unsigned long i;
@@ -669,7 +783,7 @@ static int verify_headers(const void *data, unsigned long size,
 	for (i = 0; i < size; i++) {
 		switch (buffer[i]) {
 		case '\0':
-			return report(options, obj,
+			return report(options, oid, type,
 				FSCK_MSG_NUL_IN_HEADER,
 				"unterminated header: NUL at offset %ld", i);
 		case '\n':
@@ -687,11 +801,13 @@ static int verify_headers(const void *data, unsigned long size,
 	if (size && buffer[size - 1] == '\n')
 		return 0;
 
-	return report(options, obj,
+	return report(options, oid, type,
 		FSCK_MSG_UNTERMINATED_HEADER, "unterminated header");
 }
 
-static int fsck_ident(const char **ident, struct object *obj, struct fsck_options *options)
+static int fsck_ident(const char **ident,
+		      const struct object_id *oid, enum object_type type,
+		      struct fsck_options *options)
 {
 	const char *p = *ident;
 	char *end;
@@ -701,28 +817,28 @@ static int fsck_ident(const char **ident, struct object *obj, struct fsck_option
 		(*ident)++;
 
 	if (*p == '<')
-		return report(options, obj, FSCK_MSG_MISSING_NAME_BEFORE_EMAIL, "invalid author/committer line - missing space before email");
+		return report(options, oid, type, FSCK_MSG_MISSING_NAME_BEFORE_EMAIL, "invalid author/committer line - missing space before email");
 	p += strcspn(p, "<>\n");
 	if (*p == '>')
-		return report(options, obj, FSCK_MSG_BAD_NAME, "invalid author/committer line - bad name");
+		return report(options, oid, type, FSCK_MSG_BAD_NAME, "invalid author/committer line - bad name");
 	if (*p != '<')
-		return report(options, obj, FSCK_MSG_MISSING_EMAIL, "invalid author/committer line - missing email");
+		return report(options, oid, type, FSCK_MSG_MISSING_EMAIL, "invalid author/committer line - missing email");
 	if (p[-1] != ' ')
-		return report(options, obj, FSCK_MSG_MISSING_SPACE_BEFORE_EMAIL, "invalid author/committer line - missing space before email");
+		return report(options, oid, type, FSCK_MSG_MISSING_SPACE_BEFORE_EMAIL, "invalid author/committer line - missing space before email");
 	p++;
 	p += strcspn(p, "<>\n");
 	if (*p != '>')
-		return report(options, obj, FSCK_MSG_BAD_EMAIL, "invalid author/committer line - bad email");
+		return report(options, oid, type, FSCK_MSG_BAD_EMAIL, "invalid author/committer line - bad email");
 	p++;
 	if (*p != ' ')
-		return report(options, obj, FSCK_MSG_MISSING_SPACE_BEFORE_DATE, "invalid author/committer line - missing space before date");
+		return report(options, oid, type, FSCK_MSG_MISSING_SPACE_BEFORE_DATE, "invalid author/committer line - missing space before date");
 	p++;
 	if (*p == '0' && p[1] != ' ')
-		return report(options, obj, FSCK_MSG_ZERO_PADDED_DATE, "invalid author/committer line - zero-padded date");
+		return report(options, oid, type, FSCK_MSG_ZERO_PADDED_DATE, "invalid author/committer line - zero-padded date");
 	if (date_overflows(parse_timestamp(p, &end, 10)))
-		return report(options, obj, FSCK_MSG_BAD_DATE_OVERFLOW, "invalid author/committer line - date causes integer overflow");
+		return report(options, oid, type, FSCK_MSG_BAD_DATE_OVERFLOW, "invalid author/committer line - date causes integer overflow");
 	if ((end == p || *end != ' '))
-		return report(options, obj, FSCK_MSG_BAD_DATE, "invalid author/committer line - bad date");
+		return report(options, oid, type, FSCK_MSG_BAD_DATE, "invalid author/committer line - bad date");
 	p = end + 1;
 	if ((*p != '+' && *p != '-') ||
 	    !isdigit(p[1]) ||
@@ -730,83 +846,60 @@ static int fsck_ident(const char **ident, struct object *obj, struct fsck_option
 	    !isdigit(p[3]) ||
 	    !isdigit(p[4]) ||
 	    (p[5] != '\n'))
-		return report(options, obj, FSCK_MSG_BAD_TIMEZONE, "invalid author/committer line - bad time zone");
+		return report(options, oid, type, FSCK_MSG_BAD_TIMEZONE, "invalid author/committer line - bad time zone");
 	p += 6;
 	return 0;
 }
 
-static int fsck_commit_buffer(struct commit *commit, const char *buffer,
-	unsigned long size, struct fsck_options *options)
+static int fsck_commit(const struct object_id *oid,
+		       const char *buffer, unsigned long size,
+		       struct fsck_options *options)
 {
-	struct object_id tree_oid, oid;
-	struct commit_graft *graft;
-	unsigned parent_count, parent_line_count = 0, author_count;
+	struct object_id tree_oid, parent_oid;
+	unsigned author_count;
 	int err;
 	const char *buffer_begin = buffer;
 	const char *p;
 
-	if (verify_headers(buffer, size, &commit->object, options))
+	if (verify_headers(buffer, size, oid, OBJ_COMMIT, options))
 		return -1;
 
 	if (!skip_prefix(buffer, "tree ", &buffer))
-		return report(options, &commit->object, FSCK_MSG_MISSING_TREE, "invalid format - expected 'tree' line");
+		return report(options, oid, OBJ_COMMIT, FSCK_MSG_MISSING_TREE, "invalid format - expected 'tree' line");
 	if (parse_oid_hex(buffer, &tree_oid, &p) || *p != '\n') {
-		err = report(options, &commit->object, FSCK_MSG_BAD_TREE_SHA1, "invalid 'tree' line format - bad sha1");
+		err = report(options, oid, OBJ_COMMIT, FSCK_MSG_BAD_TREE_SHA1, "invalid 'tree' line format - bad sha1");
 		if (err)
 			return err;
 	}
 	buffer = p + 1;
 	while (skip_prefix(buffer, "parent ", &buffer)) {
-		if (parse_oid_hex(buffer, &oid, &p) || *p != '\n') {
-			err = report(options, &commit->object, FSCK_MSG_BAD_PARENT_SHA1, "invalid 'parent' line format - bad sha1");
+		if (parse_oid_hex(buffer, &parent_oid, &p) || *p != '\n') {
+			err = report(options, oid, OBJ_COMMIT, FSCK_MSG_BAD_PARENT_SHA1, "invalid 'parent' line format - bad sha1");
 			if (err)
 				return err;
 		}
 		buffer = p + 1;
-		parent_line_count++;
-	}
-	graft = lookup_commit_graft(the_repository, &commit->object.oid);
-	parent_count = commit_list_count(commit->parents);
-	if (graft) {
-		if (graft->nr_parent == -1 && !parent_count)
-			; /* shallow commit */
-		else if (graft->nr_parent != parent_count) {
-			err = report(options, &commit->object, FSCK_MSG_MISSING_GRAFT, "graft objects missing");
-			if (err)
-				return err;
-		}
-	} else {
-		if (parent_count != parent_line_count) {
-			err = report(options, &commit->object, FSCK_MSG_MISSING_PARENT, "parent objects missing");
-			if (err)
-				return err;
-		}
 	}
 	author_count = 0;
 	while (skip_prefix(buffer, "author ", &buffer)) {
 		author_count++;
-		err = fsck_ident(&buffer, &commit->object, options);
+		err = fsck_ident(&buffer, oid, OBJ_COMMIT, options);
 		if (err)
 			return err;
 	}
 	if (author_count < 1)
-		err = report(options, &commit->object, FSCK_MSG_MISSING_AUTHOR, "invalid format - expected 'author' line");
+		err = report(options, oid, OBJ_COMMIT, FSCK_MSG_MISSING_AUTHOR, "invalid format - expected 'author' line");
 	else if (author_count > 1)
-		err = report(options, &commit->object, FSCK_MSG_MULTIPLE_AUTHORS, "invalid format - multiple 'author' lines");
+		err = report(options, oid, OBJ_COMMIT, FSCK_MSG_MULTIPLE_AUTHORS, "invalid format - multiple 'author' lines");
 	if (err)
 		return err;
 	if (!skip_prefix(buffer, "committer ", &buffer))
-		return report(options, &commit->object, FSCK_MSG_MISSING_COMMITTER, "invalid format - expected 'committer' line");
-	err = fsck_ident(&buffer, &commit->object, options);
+		return report(options, oid, OBJ_COMMIT, FSCK_MSG_MISSING_COMMITTER, "invalid format - expected 'committer' line");
+	err = fsck_ident(&buffer, oid, OBJ_COMMIT, options);
 	if (err)
 		return err;
-	if (!get_commit_tree(commit)) {
-		err = report(options, &commit->object, FSCK_MSG_BAD_TREE, "could not load commit's tree %s", oid_to_hex(&tree_oid));
-		if (err)
-			return err;
-	}
 	if (memchr(buffer_begin, '\0', size)) {
-		err = report(options, &commit->object, FSCK_MSG_NUL_IN_COMMIT,
+		err = report(options, oid, OBJ_COMMIT, FSCK_MSG_NUL_IN_COMMIT,
 			     "NUL byte in the commit object body");
 		if (err)
 			return err;
@@ -814,91 +907,60 @@ static int fsck_commit_buffer(struct commit *commit, const char *buffer,
 	return 0;
 }
 
-static int fsck_commit(struct commit *commit, const char *data,
-	unsigned long size, struct fsck_options *options)
-{
-	const char *buffer = data ?  data : get_commit_buffer(commit, &size);
-	int ret = fsck_commit_buffer(commit, buffer, size, options);
-	if (!data)
-		unuse_commit_buffer(commit, buffer);
-	return ret;
-}
-
-static int fsck_tag_buffer(struct tag *tag, const char *data,
-	unsigned long size, struct fsck_options *options)
+static int fsck_tag(const struct object_id *oid, const char *buffer,
+		    unsigned long size, struct fsck_options *options)
 {
-	struct object_id oid;
+	struct object_id tagged_oid;
 	int ret = 0;
-	const char *buffer;
-	char *to_free = NULL, *eol;
+	char *eol;
 	struct strbuf sb = STRBUF_INIT;
 	const char *p;
 
-	if (data)
-		buffer = data;
-	else {
-		enum object_type type;
-
-		buffer = to_free =
-			read_object_file(&tag->object.oid, &type, &size);
-		if (!buffer)
-			return report(options, &tag->object,
-				FSCK_MSG_MISSING_TAG_OBJECT,
-				"cannot read tag object");
-
-		if (type != OBJ_TAG) {
-			ret = report(options, &tag->object,
-				FSCK_MSG_TAG_OBJECT_NOT_TAG,
-				"expected tag got %s",
-			    type_name(type));
-			goto done;
-		}
-	}
-
-	ret = verify_headers(buffer, size, &tag->object, options);
+	ret = verify_headers(buffer, size, oid, OBJ_TAG, options);
 	if (ret)
 		goto done;
 
 	if (!skip_prefix(buffer, "object ", &buffer)) {
-		ret = report(options, &tag->object, FSCK_MSG_MISSING_OBJECT, "invalid format - expected 'object' line");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_OBJECT, "invalid format - expected 'object' line");
 		goto done;
 	}
-	if (parse_oid_hex(buffer, &oid, &p) || *p != '\n') {
-		ret = report(options, &tag->object, FSCK_MSG_BAD_OBJECT_SHA1, "invalid 'object' line format - bad sha1");
+	if (parse_oid_hex(buffer, &tagged_oid, &p) || *p != '\n') {
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_BAD_OBJECT_SHA1, "invalid 'object' line format - bad sha1");
 		if (ret)
 			goto done;
 	}
 	buffer = p + 1;
 
 	if (!skip_prefix(buffer, "type ", &buffer)) {
-		ret = report(options, &tag->object, FSCK_MSG_MISSING_TYPE_ENTRY, "invalid format - expected 'type' line");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TYPE_ENTRY, "invalid format - expected 'type' line");
 		goto done;
 	}
 	eol = strchr(buffer, '\n');
 	if (!eol) {
-		ret = report(options, &tag->object, FSCK_MSG_MISSING_TYPE, "invalid format - unexpected end after 'type' line");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TYPE, "invalid format - unexpected end after 'type' line");
 		goto done;
 	}
 	if (type_from_string_gently(buffer, eol - buffer, 1) < 0)
-		ret = report(options, &tag->object, FSCK_MSG_BAD_TYPE, "invalid 'type' value");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_BAD_TYPE, "invalid 'type' value");
 	if (ret)
 		goto done;
 	buffer = eol + 1;
 
 	if (!skip_prefix(buffer, "tag ", &buffer)) {
-		ret = report(options, &tag->object, FSCK_MSG_MISSING_TAG_ENTRY, "invalid format - expected 'tag' line");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TAG_ENTRY, "invalid format - expected 'tag' line");
 		goto done;
 	}
 	eol = strchr(buffer, '\n');
 	if (!eol) {
-		ret = report(options, &tag->object, FSCK_MSG_MISSING_TAG, "invalid format - unexpected end after 'type' line");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TAG, "invalid format - unexpected end after 'type' line");
 		goto done;
 	}
 	strbuf_addf(&sb, "refs/tags/%.*s", (int)(eol - buffer), buffer);
 	if (check_refname_format(sb.buf, 0)) {
-		ret = report(options, &tag->object, FSCK_MSG_BAD_TAG_NAME,
-			   "invalid 'tag' name: %.*s",
-			   (int)(eol - buffer), buffer);
+		ret = report(options, oid, OBJ_TAG,
+			     FSCK_MSG_BAD_TAG_NAME,
+			     "invalid 'tag' name: %.*s",
+			     (int)(eol - buffer), buffer);
 		if (ret)
 			goto done;
 	}
@@ -906,32 +968,163 @@ static int fsck_tag_buffer(struct tag *tag, const char *data,
 
 	if (!skip_prefix(buffer, "tagger ", &buffer)) {
 		/* early tags do not contain 'tagger' lines; warn only */
-		ret = report(options, &tag->object, FSCK_MSG_MISSING_TAGGER_ENTRY, "invalid format - expected 'tagger' line");
+		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TAGGER_ENTRY, "invalid format - expected 'tagger' line");
 		if (ret)
 			goto done;
 	}
 	else
-		ret = fsck_ident(&buffer, &tag->object, options);
+		ret = fsck_ident(&buffer, oid, OBJ_TAG, options);
 
 done:
 	strbuf_release(&sb);
-	free(to_free);
 	return ret;
 }
 
-static int fsck_tag(struct tag *tag, const char *data,
-	unsigned long size, struct fsck_options *options)
+/*
+ * Like builtin/submodule--helper.c's starts_with_dot_slash, but without
+ * relying on the platform-dependent is_dir_sep helper.
+ *
+ * This is for use in checking whether a submodule URL is interpreted as
+ * relative to the current directory on any platform, since \ is a
+ * directory separator on Windows but not on other platforms.
+ */
+static int starts_with_dot_slash(const char *str)
 {
-	struct object *tagged = tag->tagged;
+	return str[0] == '.' && (str[1] == '/' || str[1] == '\\');
+}
 
-	if (!tagged)
-		return report(options, &tag->object, FSCK_MSG_BAD_TAG_OBJECT, "could not load tagged object");
+/*
+ * Like starts_with_dot_slash, this is a variant of submodule--helper's
+ * helper of the same name with the twist that it accepts backslash as a
+ * directory separator even on non-Windows platforms.
+ */
+static int starts_with_dot_dot_slash(const char *str)
+{
+	return str[0] == '.' && starts_with_dot_slash(str + 1);
+}
 
-	return fsck_tag_buffer(tag, data, size, options);
+static int submodule_url_is_relative(const char *url)
+{
+	return starts_with_dot_slash(url) || starts_with_dot_dot_slash(url);
+}
+
+/*
+ * Count directory components that a relative submodule URL should chop
+ * from the remote_url it is to be resolved against.
+ *
+ * In other words, this counts "../" components at the start of a
+ * submodule URL.
+ *
+ * Returns the number of directory components to chop and writes a
+ * pointer to the next character of url after all leading "./" and
+ * "../" components to out.
+ */
+static int count_leading_dotdots(const char *url, const char **out)
+{
+	int result = 0;
+	while (1) {
+		if (starts_with_dot_dot_slash(url)) {
+			result++;
+			url += strlen("../");
+			continue;
+		}
+		if (starts_with_dot_slash(url)) {
+			url += strlen("./");
+			continue;
+		}
+		*out = url;
+		return result;
+	}
+}
+/*
+ * Check whether a transport is implemented by git-remote-curl.
+ *
+ * If it is, returns 1 and writes the URL that would be passed to
+ * git-remote-curl to the "out" parameter.
+ *
+ * Otherwise, returns 0 and leaves "out" untouched.
+ *
+ * Examples:
+ *   http::https://example.com/repo.git -> 1, https://example.com/repo.git
+ *   https://example.com/repo.git -> 1, https://example.com/repo.git
+ *   git://example.com/repo.git -> 0
+ *
+ * This is for use in checking for previously exploitable bugs that
+ * required a submodule URL to be passed to git-remote-curl.
+ */
+static int url_to_curl_url(const char *url, const char **out)
+{
+	/*
+	 * We don't need to check for case-aliases, "http.exe", and so
+	 * on because in the default configuration, is_transport_allowed
+	 * prevents URLs with those schemes from being cloned
+	 * automatically.
+	 */
+	if (skip_prefix(url, "http::", out) ||
+	    skip_prefix(url, "https::", out) ||
+	    skip_prefix(url, "ftp::", out) ||
+	    skip_prefix(url, "ftps::", out))
+		return 1;
+	if (starts_with(url, "http://") ||
+	    starts_with(url, "https://") ||
+	    starts_with(url, "ftp://") ||
+	    starts_with(url, "ftps://")) {
+		*out = url;
+		return 1;
+	}
+	return 0;
+}
+
+static int check_submodule_url(const char *url)
+{
+	const char *curl_url;
+
+	if (looks_like_command_line_option(url))
+		return -1;
+
+	if (submodule_url_is_relative(url)) {
+		char *decoded;
+		const char *next;
+		int has_nl;
+
+		/*
+		 * This could be appended to an http URL and url-decoded;
+		 * check for malicious characters.
+		 */
+		decoded = url_decode(url);
+		has_nl = !!strchr(decoded, '\n');
+
+		free(decoded);
+		if (has_nl)
+			return -1;
+
+		/*
+		 * URLs which escape their root via "../" can overwrite
+		 * the host field and previous components, resolving to
+		 * URLs like https::example.com/submodule.git and
+		 * https:///example.com/submodule.git that were
+		 * susceptible to CVE-2020-11008.
+		 */
+		if (count_leading_dotdots(url, &next) > 0 &&
+		    (*next == ':' || *next == '/'))
+			return -1;
+	}
+
+	else if (url_to_curl_url(url, &curl_url)) {
+		struct credential c = CREDENTIAL_INIT;
+		int ret = 0;
+		if (credential_from_url_gently(&c, curl_url, 1) ||
+		    !*c.host)
+			ret = -1;
+		credential_clear(&c);
+		return ret;
+	}
+
+	return 0;
 }
 
 struct fsck_gitmodules_data {
-	struct object *obj;
+	const struct object_id *oid;
 	struct fsck_options *options;
 	int ret;
 };
@@ -940,7 +1133,7 @@ static int fsck_gitmodules_fn(const char *var, const char *value, void *vdata)
 {
 	struct fsck_gitmodules_data *data = vdata;
 	const char *subsection, *key;
-	int subsection_len;
+	size_t subsection_len;
 	char *name;
 
 	if (parse_config_key(var, "submodule", &subsection, &subsection_len, &key) < 0 ||
@@ -949,38 +1142,47 @@ static int fsck_gitmodules_fn(const char *var, const char *value, void *vdata)
 
 	name = xmemdupz(subsection, subsection_len);
 	if (check_submodule_name(name) < 0)
-		data->ret |= report(data->options, data->obj,
+		data->ret |= report(data->options,
+				    data->oid, OBJ_BLOB,
 				    FSCK_MSG_GITMODULES_NAME,
 				    "disallowed submodule name: %s",
 				    name);
 	if (!strcmp(key, "url") && value &&
-	    looks_like_command_line_option(value))
-		data->ret |= report(data->options, data->obj,
+	    check_submodule_url(value) < 0)
+		data->ret |= report(data->options,
+				    data->oid, OBJ_BLOB,
 				    FSCK_MSG_GITMODULES_URL,
 				    "disallowed submodule url: %s",
 				    value);
 	if (!strcmp(key, "path") && value &&
 	    looks_like_command_line_option(value))
-		data->ret |= report(data->options, data->obj,
+		data->ret |= report(data->options,
+				    data->oid, OBJ_BLOB,
 				    FSCK_MSG_GITMODULES_PATH,
 				    "disallowed submodule path: %s",
 				    value);
+	if (!strcmp(key, "update") && value &&
+	    parse_submodule_update_type(value) == SM_UPDATE_COMMAND)
+		data->ret |= report(data->options, data->oid, OBJ_BLOB,
+				    FSCK_MSG_GITMODULES_UPDATE,
+				    "disallowed submodule update setting: %s",
+				    value);
 	free(name);
 
 	return 0;
 }
 
-static int fsck_blob(struct blob *blob, const char *buf,
+static int fsck_blob(const struct object_id *oid, const char *buf,
 		     unsigned long size, struct fsck_options *options)
 {
 	struct fsck_gitmodules_data data;
 	struct config_options config_opts = { 0 };
 
-	if (!oidset_contains(&gitmodules_found, &blob->object.oid))
+	if (!oidset_contains(&gitmodules_found, oid))
 		return 0;
-	oidset_insert(&gitmodules_done, &blob->object.oid);
+	oidset_insert(&gitmodules_done, oid);
 
-	if (object_on_skiplist(options, &blob->object))
+	if (object_on_skiplist(options, oid))
 		return 0;
 
 	if (!buf) {
@@ -989,18 +1191,18 @@ static int fsck_blob(struct blob *blob, const char *buf,
 		 * blob too gigantic to load into memory. Let's just consider
 		 * that an error.
 		 */
-		return report(options, &blob->object,
+		return report(options, oid, OBJ_BLOB,
 			      FSCK_MSG_GITMODULES_LARGE,
 			      ".gitmodules too large to parse");
 	}
 
-	data.obj = &blob->object;
+	data.oid = oid;
 	data.options = options;
 	data.ret = 0;
 	config_opts.error_action = CONFIG_ERROR_SILENT;
 	if (git_config_from_mem(fsck_gitmodules_fn, CONFIG_ORIGIN_BLOB,
 				".gitmodules", buf, size, &data, &config_opts))
-		data.ret |= report(options, &blob->object,
+		data.ret |= report(options, oid, OBJ_BLOB,
 				   FSCK_MSG_GITMODULES_PARSE,
 				   "could not parse gitmodules blob");
 
@@ -1011,31 +1213,33 @@ int fsck_object(struct object *obj, void *data, unsigned long size,
 	struct fsck_options *options)
 {
 	if (!obj)
-		return report(options, obj, FSCK_MSG_BAD_OBJECT_SHA1, "no valid object to fsck");
+		return report(options, NULL, OBJ_NONE, FSCK_MSG_BAD_OBJECT_SHA1, "no valid object to fsck");
 
 	if (obj->type == OBJ_BLOB)
-		return fsck_blob((struct blob *)obj, data, size, options);
+		return fsck_blob(&obj->oid, data, size, options);
 	if (obj->type == OBJ_TREE)
-		return fsck_tree((struct tree *) obj, options);
+		return fsck_tree(&obj->oid, data, size, options);
 	if (obj->type == OBJ_COMMIT)
-		return fsck_commit((struct commit *) obj, (const char *) data,
-			size, options);
+		return fsck_commit(&obj->oid, data, size, options);
 	if (obj->type == OBJ_TAG)
-		return fsck_tag((struct tag *) obj, (const char *) data,
-			size, options);
+		return fsck_tag(&obj->oid, data, size, options);
 
-	return report(options, obj, FSCK_MSG_UNKNOWN_TYPE, "unknown type '%d' (internal fsck error)",
-			  obj->type);
+	return report(options, &obj->oid, obj->type,
+		      FSCK_MSG_UNKNOWN_TYPE,
+		      "unknown type '%d' (internal fsck error)",
+		      obj->type);
 }
 
 int fsck_error_function(struct fsck_options *o,
-	struct object *obj, int msg_type, const char *message)
+			const struct object_id *oid,
+			enum object_type object_type,
+			int msg_type, const char *message)
 {
 	if (msg_type == FSCK_WARN) {
-		warning("object %s: %s", describe_object(o, obj), message);
+		warning("object %s: %s", fsck_describe_object(o, oid), message);
 		return 0;
 	}
-	error("object %s: %s", describe_object(o, obj), message);
+	error("object %s: %s", fsck_describe_object(o, oid), message);
 	return 1;
 }
 
@@ -1047,7 +1251,6 @@ int fsck_finish(struct fsck_options *options)
 
 	oidset_iter_init(&gitmodules_found, &iter);
 	while ((oid = oidset_iter_next(&iter))) {
-		struct blob *blob;
 		enum object_type type;
 		unsigned long size;
 		char *buf;
@@ -1055,29 +1258,22 @@ int fsck_finish(struct fsck_options *options)
 		if (oidset_contains(&gitmodules_done, oid))
 			continue;
 
-		blob = lookup_blob(the_repository, oid);
-		if (!blob) {
-			struct object *obj = lookup_unknown_object(oid);
-			ret |= report(options, obj,
-				      FSCK_MSG_GITMODULES_BLOB,
-				      "non-blob found at .gitmodules");
-			continue;
-		}
-
 		buf = read_object_file(oid, &type, &size);
 		if (!buf) {
-			if (is_promisor_object(&blob->object.oid))
+			if (is_promisor_object(oid))
 				continue;
-			ret |= report(options, &blob->object,
+			ret |= report(options,
+				      oid, OBJ_BLOB,
 				      FSCK_MSG_GITMODULES_MISSING,
 				      "unable to read .gitmodules blob");
 			continue;
 		}
 
 		if (type == OBJ_BLOB)
-			ret |= fsck_blob(blob, buf, size, options);
+			ret |= fsck_blob(oid, buf, size, options);
 		else
-			ret |= report(options, &blob->object,
+			ret |= report(options,
+				      oid, type,
 				      FSCK_MSG_GITMODULES_BLOB,
 				      "non-blob found at .gitmodules");
 		free(buf);