From bcaec0456e20d69fd35784543c6d80401f4d6754 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 25 Aug 2017 11:26:31 +0100
Subject: [PATCH] git-debrebase: downstream-rebase-launder-v0 first cut

---
 git-debrebase | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/git-debrebase b/git-debrebase
index a1d277e5..c3ff3afb 100755
--- a/git-debrebase
+++ b/git-debrebase
@@ -716,6 +716,51 @@ sub cmd_analyse () {
     STDOUT->error and die $!;
 }
 
+sub cmd_downstream_rebase_launder_v0 () {
+    badusage "needs 1 argument, the baseline" unless @ARGV=0;
+    my ($base) = @ARGV;
+    $base = git_rev_parse $base;
+    my $old_head = get_head();
+    my $current = $old_head;
+    my $topmost_keep;
+    for (;;) {
+	if ($current eq $base) {
+	    $topmust_keep //= $current;
+	    print "$current BASE: stopping\n";
+	    last;
+	}
+	my $cl = classify $current;
+	print " $current $cl->{Type}";
+	my $keep = 0;
+	my $p0 = $cl->{Parents}[0]{CommitId};
+	if ($cl->{Type} eq 'Pseudomerge') {
+	    $current = $cl->{Contributor}{CommitId};
+	    print " ^".($cl->{Contributor}{Ix}+1);
+	} elsif ($cl->{Type} eq 'AddPatches' or
+		 $cl->{Type} eq 'Changelog') {
+	    print " strip";
+	    $current = $p0;
+	} else {
+	    print " keep";
+	    $current = $p0;
+	    $keep = 1;
+	}
+	print "\n";
+	if ($keep) {
+	    $topmost_keep //= $current;
+	} else {
+	    die "to-be stripped changes not on top of the branch\n"
+		if $topmost_unstripped;
+	}
+    }
+    if ($topmost_keep eq $old_head) {
+	print "unchanged\n";
+    } else {
+	print "updating to $topmost_keep\n";
+	update_head $old_head, $topmost_keep, 'downstream-rebase-launder-v0';
+    }
+}
+
 GetOptions("D+" => \$debuglevel) or die badusage "bad options\n";
 initdebug('git-debrebase ');
 enabledebug if $debuglevel;
-- 
2.30.2