git-debrebase: merge: Refactor interchange merge-base computation

[dgit.git] / git-debrebase

diff --git a/git-debrebase b/git-debrebase
index 35b75cd67ea2bc6de01e68a3621dc919efe96ce2..f93adefc49e830a09d8422df95673e42099ff1d2 100755 (executable)
--- a/git-debrebase
+++ b/git-debrebase
@@ -846,6 +846,8 @@ sub mergedbreakwaters_anchor ($) {
        $best_anchor = $panchor
            if !defined $best_anchor
            or is_fast_fwd $best_anchor, $panchor;
+       fail "inconsistent anchors in merged-breakwaters $p->{CommitId}"
+           unless is_fast_fwd $panchor, $best_anchor;
     }
     return $best_anchor;
 }
@@ -1197,7 +1199,7 @@ sub walk ($;$$$) {
            foreach my $p (@$ps) {
                $prline->(" VanillaMerge ".$p->{Ix});
                if (!is_fast_fwd $p->{Anchor}, $best_anchor) {
-                   $nomerge->('DivergentAnchor');
+                   $nomerge->('divergent anchors');
                } elsif ($p->{Anchor} eq $best_anchor) {
                    print $report " SameAnchor" if $report;
                } else {
@@ -1215,14 +1217,14 @@ sub walk ($;$$$) {
            }
 
            if ($ok && $might_be_in_bw) {
+               # We could rewrite this to contaion the metadata
+               # declaring it to be MergedBreakwaters, but
+               # unnecessarily rewriting a merge seems unhelpful.
                $prline->(" VanillaMerge MergedBreakwaters");
                $last_anchor = $best_anchor;
                $build_start->('MergedBreakwaters', $cur);
            }
 
-           $nomerge->("alleged merged-breakwater is not a breakwater")
-               unless $ty eq 'VanillaMerge';
-
            my $bwb = cmdoutput @bwbcmd;
 
            # OK, now we have a breakwater base, but we need the merge
@@ -1233,12 +1235,22 @@ sub walk ($;$$$) {
            # breakwater merge base as an ancestor.
 
            my @ibs =
-               grep { is_fast_fwd $bwb, $_ }
                grep /./,
                split /\n/,
                cmdoutput @ibcmd;
-           my ($ib) = @ibs
-               or $nomerge->("no suitable interchange merge base");
+
+            @ibs or confess 'internal error, expected anchor at least ?';
+
+           my $ib;
+           foreach my $tibix (0..$#ibs) {
+               my $tib = $ibs[$tibix];
+               my $ff = is_fast_fwd $bwb, $tib;
+               next unless $ff;
+               next if $ib;
+               $ib = $tib;
+           }
+
+           $ib or $nomerge->("no suitable interchange merge base");
 
            $prline->("  VanillaMerge Base");
            $prprdelim->();