Teach update-index to read from ls-tree.

git-update-index --index-info can almost be usable to read from ls-tree
output to update the index (and not the working tree file) to HEAD commit,
but not quite.  It was designed to read from git-apply --index-info
output, and does not want " blob " in ls-tree output.  Accept that as well.

This lets us update "git-checkout <ent> <path>" that used to filter the
extra " blob " string out.  Noted by Luben.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-checkout.sh

@@ -82,7 +82,6 @@ then
 		# rescuing paths and is never meant to remove what
 		# is not in the named tree-ish.
 		git-ls-tree -r "$new" "$@" |
-		sed -ne 's/^\([0-7]*\) blob \(.*\)$/\1 \2/p' |
 		git-update-index --index-info || exit $?
 	fi
 	git-checkout-index -f -u -- "$@"

update-index.c

@@ -338,7 +338,7 @@ static void read_index_info(int line_termination)
 	struct strbuf buf;
 	strbuf_init(&buf);
 	while (1) {
-		char *ptr;
+		char *ptr, *tab;
 		char *path_name;
 		unsigned char sha1[20];
 		unsigned int mode;
@@ -348,12 +348,15 @@ static void read_index_info(int line_termination)
 			break;
 
 		mode = strtoul(buf.buf, &ptr, 8);
-		if (ptr == buf.buf || *ptr != ' ' ||
-		    get_sha1_hex(ptr + 1, sha1) ||
-		    ptr[41] != '\t')
+		if (ptr == buf.buf || *ptr != ' ')
 			goto bad_line;
 
-		ptr += 42;
+		tab = strchr(ptr, '\t');
+		if (!tab || tab - ptr < 41)
+			goto bad_line;
+		if (get_sha1_hex(tab - 40, sha1) || tab[-41] != ' ')
+			goto bad_line;
+		ptr = tab + 1;
 
 		if (line_termination && ptr[0] == '"')
 			path_name = unquote_c_style(ptr, NULL);