move tardir creation into the prep_tar function

It was annoying that the tardir was created even if the build failed due
to uncommitted changes, this avoids that problem.

scripts/Dpkg/Source/VCS/git.pm

@@ -135,7 +135,9 @@ sub prep_tar {
 
 	# TODO support for creating a shallow clone for those cases where
 	# uploading the whole repo history is not desired
-	
+
+	mkdir($tardir,0755) ||
+            &syserr(sprintf(_g("unable to create `%s'"), $tardir));
 	system("cp -a $srcdir/.git $tardir");
 	$? && main::subprocerr("cp -a $srcdir/.git $tardir");
 

scripts/dpkg-source.pl

@@ -478,14 +478,11 @@ if ($opmode eq 'build') {
 	$tarname="$basenamerev.$vcs.tar.gz";
         $tardirbase= $dirbase; $tardirname= "$tarname.tmp";
 
-        mkdir($tardirname,0755) ||
-            &syserr(sprintf(_g("unable to create `%s'"), $tardirname));
-	push @exit_handlers, sub { erasedir($tardirname) };
-        
 	eval qq{Dpkg::Source::VCS::${vcs}::prep_tar(\$dir, \$tardirname)};
 	if ($@) {
             &syserr($@);
 	}
+	push @exit_handlers, sub { erasedir($tardirname) };
     }
     elsif ($sourcestyle ne 'n') {
 	my $origdirbase = $origdir;