From c10954df2a6f7ed9f12e12f6e65049d78c9672e4 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 11 Aug 2018 16:23:22 +0100
Subject: [PATCH] git-debrebase: merge: Introduce $mwrecknote in walk analysis
 half

We collect various git objects that we may want to present to the user
as wreckage.  Currently we dump them in $cl and print them out in
$nomerge.  We'll want to do better than that of course.

Also, we don't collect any wreckage for the actual series merge yet.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 git-debrebase | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/git-debrebase b/git-debrebase
index 771410ef..2a2d1ed2 100755
--- a/git-debrebase
+++ b/git-debrebase
@@ -1029,6 +1029,11 @@ sub walk ($;$$$) {
 	fail "something useful about failed merge attempt @_ xxx".Dumper($cl);
     };
 
+    my $mwrecknote = sub {
+	my ($reftail, $commitish) = @_;
+	$cl->{MergeWreckNotes}{$reftail} = $commitish;
+    };
+
     my $last_anchor;
 
     for (;;) {
@@ -1178,6 +1183,8 @@ sub walk ($;$$$) {
 
 	    my $ps = $cl->{Parents};
 
+	    $mwrecknote->('vanilla-merge', $cl->{CommitId});
+
 	    foreach my $p (@$ps) {
 		$prline->(" VanillaMerge ".$p->{Ix});
 		$prprdelim->();
@@ -1188,6 +1195,17 @@ sub walk ($;$$$) {
 		$p->{Breakwater} = $p->{SeriesBase} = $pbw;
 		$p->{Anchor} = $panchor;
 
+		my $lr = $p->{LeftRight} = (qw(left right))[$p->{Ix}];
+		$mwrecknote->("$lr-input", $p->{CommitId});
+
+		my $mwrecknote_parent = sub {
+		    my ($which) = @_;
+		    $mwrecknote->("$lr-".(lc $which), $p->{$which});
+		};
+		$mwrecknote_parent->('Laundered');
+		$mwrecknote_parent->('Breakwater');
+		$mwrecknote_parent->('Anchor');
+
 		$best_anchor = $panchor if
 		    !defined $best_anchor or
 		    is_fast_fwd $best_anchor, $panchor;
@@ -1196,6 +1214,8 @@ sub walk ($;$$$) {
 		    " p=$panchor\n";
 	    }
 
+	    $mwrecknote->('result-anchor', $best_anchor);
+
 	    foreach my $p (@$ps) {
 		$prline->(" VanillaMerge ".$p->{Ix});
 		if (!is_fast_fwd $p->{Anchor}, $best_anchor) {
@@ -1242,20 +1262,32 @@ sub walk ($;$$$) {
             @ibs or confess 'internal error, expected anchor at least ?';
 
 	    my $ib;
+	    my $ibleaf;
 	    foreach my $tibix (0..$#ibs) {
 		my $tib = $ibs[$tibix];
 		my $ff = is_fast_fwd $bwb, $tib;
+		my $ok = !$ff ? 'rej' : $ib ? 'extra' : 'ok';
+		my $tibleaf = "interchange-mbcand-$ok-$tibix";
+		$mwrecknote->($tibleaf, $tib);
 		next unless $ff;
 		next if $ib;
 		$ib = $tib;
+		$ibleaf = $tibleaf;
 	    }
 
 	    $ib or $nomerge->("no suitable interchange merge base");
 
 	    $prline->("  VanillaMerge Base");
 	    $prprdelim->();
-	    my ($btip, $bbw, $banchor) =
+	    my ($btip, $bbw, $banchor) = eval {
 		walk $ib, 0, $report, $report_lprefix.'  ';
+	    };
+	    $nomerge->("walking interchange branch merge base ($ibleaf): ".
+		       $@) if length $@;
+
+	    $mwrecknote->("mergebase-laundered", $btip);
+	    $mwrecknote->("mergebase-breakwater", $bbw);
+	    $mwrecknote->("mergebase-anchor", $banchor);
 
 	    my $ibinfo = { SeriesTip => $btip,
 			   SeriesBase => $bbw,
-- 
2.30.2