Move is_fast_fwd into Dgit.pm

1 files changed, 13 insertions, 1 deletions

diff --git a/Debian/Dgit.pm b/Debian/Dgit.pm
index 2c9c9f9..f20f1bc 100644
--- a/Debian/Dgit.pm
+++ b/Debian/Dgit.pm
@@ -19,7 +19,7 @@ BEGIN {
                       stat_exists fail waitstatusmsg failedcmd
                       cmdoutput cmdoutput_errok
                       git_rev_parse git_for_each_ref
-                      git_for_each_tag_referring
+                      git_for_each_tag_referring is_fast_fwd
                       $package_re $component_re $deliberately_re
                       $branchprefix
                       initdebug enabledebug enabledebuglevel
@@ -211,4 +211,16 @@ sub git_for_each_tag_referring ($$) {
     });
 }
 
+sub is_fast_fwd ($$) {
+    my ($ancestor,$child) = @_;
+    my @cmd = (qw(git merge-base), $ancestor, $child);
+    my $mb = cmdoutput_errok @cmd;
+    if (defined $mb) {
+	return git_rev_parse($mb) eq git_rev_parse($ancestor);
+    } else {
+	$?==256 or failedcmd @cmd;
+	return 0;
+    }
+}
+
 1;