pkgbase: examine METALOG files relative to stage root directory

Previously we stripped the '.' from the beginning of each METALOG entry
to determine the path to stat.  This meant that we examined files on the
build host, not the staged files.

Instead, strip off the last part of the specified METALOG pathname to
find the stage root directory, and stat files relative to that.

Reviewed by:	bapt
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D37412

tools/pkgbase/metalog_reader.lua

@@ -257,6 +257,7 @@ end
 --- @param verbose boolean
 --- @param w_notagdirs boolean turn on to also check directories
 function Analysis_session(metalog, verbose, w_notagdirs)
+	local stage_root = {}
 	local files = {} -- map<string, MetalogRow[]>
 	-- set is map<elem, bool>. if bool is true then elem exists
 	local pkgs = {} -- map<string, set<string>>
@@ -418,17 +419,14 @@ function Analysis_session(metalog, verbose, w_notagdirs)
 			if files[filename][1].attrs.type ~= 'file' then
 				goto continue
 			end
-			-- make ./xxx become /xxx so that we can stat
+			local fs = attributes(stage_root .. filename)
-			filename = filename:sub(2)
-			local fs = attributes(filename)
 			if fs == nil then
 				unstatables[#unstatables+1] = filename
 				goto continue
 			end
 			local inode = fs.ino
 			inm[inode] = inm[inode] or {}
-			-- add back the dot prefix
+			table.insert(inm[inode], filename)
-			table.insert(inm[inode], '.'..filename)
 			::continue::
 		end
 
@@ -462,6 +460,9 @@ function Analysis_session(metalog, verbose, w_notagdirs)
 		return table.concat(warn, ''), table.concat(errs, '')
 	end
 
+	-- The METALOG file is assumed to be at the top of the stage directory.
+	stage_root = string.gsub(metalog, '/[^/]*$', '/')
+
 	do
 	local fp, errmsg, errcode = io.open(metalog, 'r')
 	if fp == nil then