+ my @identical = grep { !$_->{Differs} } @p;
+ my ($stype, $series) = git_cat_file "$t:debian/patches/series";
+ my $haspatches = $stype ne 'missing' && $series =~ m/^\s*[^#\n\t ]/m;
+
+ if ($r->{Msg} =~ m{^\[git-debrebase anchor.*\]$}m) {
+ # multi-orig upstreams are represented with an anchor merge
+ # from a single upstream commit which combines the orig tarballs
+
+ my $badanchor = sub { $unknown->("git-debrebase \`anchor' but @_"); };
+ @p == 2 or return $badanchor->("has other than two parents");
+ $haspatches and return $badanchor->("contains debian/patches");
+
+ # How to decide about l/r ordering of anchors ? git
+ # --topo-order prefers to expand 2nd parent first. There's
+ # already an easy rune to look for debian/ history anyway (git log
+ # debian/) so debian breakwater branch should be 1st parent; that
+ # way also there's also an easy rune to look for the upstream
+ # patches (--topo-order).
+
+ $p[0]{IsOrigin} and $badanchor->("is an origin commit");
+ $p[1]{Differs} & ~DS_DEB and
+ $badanchor->("upstream files differ from left parent");
+ $p[0]{Differs} & ~D_UPS and
+ $badanchor->("debian/ differs from right parent");
+
+ return $classify->(qw(Anchor),
+ OrigParents => [ $p[1] ]);
+ }