git-debrebase: convert-from-gbp: Check separately for $dtag

This allows us to print a more sensible error message, Previously
git would print a fatal error, after which we carry on.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/git-debrebase b/git-debrebase
index a19d258..42e8f7e 100755
--- a/git-debrebase
+++ b/git-debrebase
@@ -2481,6 +2481,8 @@ END
 	is_fast_fwd $mtag, 'HEAD' or
 	    die "HEAD is not FF from maintainer tag $mtag!";
 	my $dtag = "archive/$mtag";
+	git_get_ref "refs/tags/$dtag" or
+	    die "dgit view tag $dtag not found\n";
 	is_fast_fwd $mtag, $dtag or
 	    die "dgit view tag $dtag is not FF from maintainer tag $mtag\n";
 	print "will stitch in dgit view, $dtag\n";