git-debrebase: Fix multi-orig handling

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/git-debrebase b/git-debrebase
index d9ceb20a24aa132d2813aab9c725807609f05bc9..fbf2a58a7188b49203ee78197b0ad406b1ced34a 100755 (executable)
--- a/git-debrebase
+++ b/git-debrebase
@@ -1202,13 +1202,29 @@ sub cmd_new_upstream_v0 () {
 
     if ($old_upstream && $old_upstream->{Msg} =~ m{^\[git-debrebase }m) {
        if ($old_upstream->{Msg} =~
- m{^\[git-debrebase upstream-combine \.((?: $extra_orig_namepart_re)+)\:.*\]$}m
+ m{^\[git-debrebase upstream-combine (\.(?: $extra_orig_namepart_re)+)\:.*\]$}m
           ) {
-           my @oldpieces = ('', split / /, $1);
-           my $parentix = -1 + scalar @{ $old_upstream->{Parents} };
-           foreach my $i (0..$#oldpieces) {
-               my $n = $oldpieces[$i];
-               $piece->($n, Old => $old_upstream->{CommitId}.'^'.$parentix);
+           my @oldpieces = (split / /, $1);
+           my $old_n_parents = scalar @{ $old_upstream->{Parents} };
+           if (@oldpieces != $old_n_parents) {
+               snag 'upstream-confusing', sprintf
+                   "previous upstream combine %s".
+                   " mentions %d pieces (each implying one orig commit)".
+                   " but has %d parents",
+                   $old_upstream->{CommitId},
+                   (scalar @oldpieces),
+                   $old_n_parents;
+           } elsif ($oldpieces[0] ne '.') {
+               snag 'upstream-confusing', sprintf
+                   "previous upstream combine %s".
+                   " first piece is not \`.'",
+                   $oldpieces[0];
+           } else {
+               $oldpieces[0] = '';
+               foreach my $i (0..$#oldpieces) {
+                   my $n = $oldpieces[$i];
+                   $piece->($n, Old => $old_upstream->{CommitId}.'^'.($i+1));
+               }
            }
        } else {
            snag 'upstream-confusing',