git-debrebase: classify: tolerate backwards breakwater merges

[dgit.git] / git-debrebase

diff --git a/git-debrebase b/git-debrebase
index b2c15d6f78e26423e5216a2b3edc7cc569e84d38..8f2e922355e440f7227a1f7afa3fd8bd8aa61753 100755 (executable)
--- a/git-debrebase
+++ b/git-debrebase
@@ -390,23 +390,32 @@ sub classify ($) {
     my ($stype, $series) = git_cat_file "$t:debian/patches/series";
     my $haspatches = $stype ne 'missing' && $series =~ m/^\s*[^#\n\t ]/m;
 
-@p = reverse @p; #xxx
-
     # How to decide about l/r ordering of breakwater merges ?  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).
-    if (@p == 2 &&
-       !$haspatches &&
-       !$p[0]{IsOrigin} && # breakwater merge never starts with an origin
-       !($p[0]{Differs} & ~D_DEB) &&
-       !($p[1]{Differs} & ~D_UPS)) {
-       return $classify->(qw(BreakwaterUpstreamMerge),
-                          OrigParents => [ $p[1] ]);
+
+    # The above tells us which way *we* will generate them.  But we
+    # might encounter ad-hoc breakwater merges generated manually,
+    # which might be the other way around.  In principle, in some odd
+    # situations, a breakwater merge might have two identical parents.
+    # In that case we guess which way round it is (ie, which parent
+    # has the upstream history).  The order of the 2-iteration loop
+    # controls which guess we make.
+
+    foreach my $prevbrw (qw(0 1)) {
+       if (@p == 2 &&
+           !$haspatches &&
+           !$p[$prevbrw]{IsOrigin} && # breakwater never starts with an origin
+           !($p[$prevbrw]{Differs} & ~D_DEB) &&
+           !($p[!$prevbrw]{Differs} & ~D_UPS)) {
+           return $classify->(qw(BreakwaterUpstreamMerge),
+                              OrigParents => [ $p[!$prevbrw] ]);
+       }
+       # xxx multi-.orig upstreams
     }
-    # xxx multi-.orig upstreams
 
     return $unknown->("complex merge");
 }