changedir_git_toplevel: Special error for not in git tree

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

1 files changed, 4 insertions, 0 deletions

diff --git a/Debian/Dgit.pm b/Debian/Dgit.pm
index bfe2ab9..458017d 100644
--- a/Debian/Dgit.pm
+++ b/Debian/Dgit.pm
@@ -502,6 +502,10 @@ sub git_rev_parse ($) {
 
 sub changedir_git_toplevel () {
     my $toplevel = cmdoutput qw(git rev-parse --show-toplevel);
+    length $toplevel or fail __ <<END;
+not in a git working tree?
+(git rev-parse --show-toplevel produced no output)
+END
     chdir $toplevel or fail f_ "chdir toplevel %s: %s\n", $toplevel, $!;
 }