+sub git_find_all_parents {
+ my ($rev) = @_;
+
+ my $revparent = open_pipe("git-rev-list","--remove-empty", "--parents","--max-count=1","$rev")
+ or die "Failed to open git-rev-list to find a single parent: $!";
+
+ my $parentline = <$revparent>;
+ chomp $parentline;
+ my ($origrev, @parents) = split m/\s+/, $parentline;
+
+ close($revparent);
+
+ return @parents;
+}
+
+sub git_merge_base {
+ my ($rev1, $rev2) = @_;
+
+ my $mb = open_pipe("git-merge-base", $rev1, $rev2)
+ or die "Failed to open git-merge-base: $!";
+
+ my $base = <$mb>;
+ chomp $base;
+
+ close($mb);
+
+ return $base;
+}
+
+# Construct a set of pseudo parents that are in the same order,
+# and the same quantity as the real parents,
+# but whose SHA1s are as similar to the logical parents
+# as possible.
+sub get_pseudo_parents {
+ my ($all, $fake) = @_;
+
+ my @all = @$all;
+ my @fake = @$fake;
+
+ my @pseudo;
+
+ my %fake = map {$_ => 1} @fake;
+ my %seenfake;
+
+ my $fakeidx = 0;
+ foreach my $p (@all) {
+ if (exists $fake{$p}) {
+ if ($fake[$fakeidx] ne $p) {
+ die sprintf("parent mismatch: %s != %s\nall:%s\nfake:%s\n",
+ $fake[$fakeidx], $p,
+ join(", ", @all),
+ join(", ", @fake),
+ );
+ }
+
+ push @pseudo, $p;
+ $fakeidx++;
+ $seenfake{$p}++;
+
+ } else {
+ my $base = git_merge_base($fake[$fakeidx], $p);
+ if ($base ne $fake[$fakeidx]) {
+ die sprintf("Result of merge-base doesn't match fake: %s,%s != %s\n",
+ $fake[$fakeidx], $p, $base);
+ }
+
+ # The details of how we parse the diffs
+ # mean that we cannot have a duplicate
+ # revision in the list, so if we've already
+ # seen the revision we would normally add, just use
+ # the actual revision.
+ if ($seenfake{$base}) {
+ push @pseudo, $p;
+ } else {
+ push @pseudo, $base;
+ $seenfake{$base}++;
+ }
+ }
+ }
+
+ return @pseudo;
+}
+