git-debrebase: new-upstream-v0: use make_commit another time (nfc)

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

diff --git a/git-debrebase b/git-debrebase
index df5d27e627b6c8093076b61e34dff6b58b834c30..db132e3f8f041f9054e572d68f5b9aed53920fda 100755 (executable)
--- a/git-debrebase
+++ b/git-debrebase
@@ -939,15 +939,12 @@ sub cmd_new_upstream_v0 () {
 
        if (@newpieces > 1) {
            # need to make the upstream subtree merge commit
-           my $us_tree = cmdoutput @git, qw(write-tree);
-           my @cmd = (@git, qw(commit-tree), $us_tree);
-           push @cmd, qw(-p), $_ foreach @upstream_merge_parents;
-           push @cmd, qw(-m), "Combine upstreams for $new_upstream_version";
-           push @cmd, qw(-m),
-               "[git-debrebase new-upstream combine . ".
-               (join " ", map { $_->{Name} } @newpieces[1..$#newpieces]).
-                "]";
-           $new_upstream = cmdoutput @cmd;
+            $new_upstream = make_commit \@upstream_merge_parents,
+                [ "Combine upstreams for $new_upstream_version",
+                  ("[git-debrebase new-upstream combine . ".
+                   (join " ", map { $_->{Name} } @newpieces[1..$#newpieces]).
+                   "]"),
+                ];
        }
 
        # $new_upstream is either the single upstream commit, or the