Reintegrate: cope with delete-modify conflicts

A more proper solution is probably to teach "rerere" to remember
what modification (probably indexed via a patch ID for flexibility,
but either the pre- or post-image blob ID without such flexibility
is probably good enough) was deemed "uninteresting" to resolve in
favor of deletion and reapply it when we see another delete-modify
conflict with the same modification, but for now, treat all
delete-modify conflict to be with uninteresting modification.

The way the Reintegrate machinery is used makes it somewhat safer
than it looks---the initial attempt to merge (and come up with a
merge-fix if needed) will always be done using "git merge" and the
resulting commit is manually examined (if only to see if there is a
need for a further merge-fix) before redo-foo script is written out
of the resulting history.  We'll need to deal with a case where a
modifying side need to be kept over the deleting side if/when it
arises, but so far I haven't seen such a case in real life.

Reintegrate

@@ -123,6 +123,27 @@ cocci_mark="treewide: apply cocci patch"
 case "$generate" in
 no)
 	accept_rerere () {
+		git ls-files -u -z |
+		perl -0 -e '
+			my %path_stage = ();
+			my @to_remove = ();
+			while (<>) {
+				my ($mode, $sha1, $stage, $path) =
+					/^([0-7]+) ([0-9a-f]+) ([0-3])	(.*)$/;
+				$path_stage{$path} ||= 0;
+				$path_stage{$path} |= (1 << ($stage - 1));
+			}
+
+			while (my ($path, $bits) = each %path_stage) {
+				if ($bits == 3 || $bits == 5) {
+					push @to_remove, $path;
+				}
+			}
+			if (@to_remove) {
+				system(qw(git rm -f), @to_remove);
+			}
+		'
+
 		if ! git write-tree 2>/dev/null >/dev/null
 		then
 			git rerere remaining