check git version requirements

This allows v1 tests to continue working on git 1.8.0 for
now.  This allows git 2.1.4 packaged with Debian 8 ("jessie")
to run old tests, at least.

I suppose it's safe to drop Debian 7 ("wheezy") due to our
dependency on git 1.8.0 for "merge-base --is-ancestor".

Writing V2 repositories requires git 2.6 for "get-mark"
support, so mask out tests for older gits.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index fd48169d..cc1ac56b 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -646,6 +646,7 @@ sub _git_log {
                                 --raw -r --no-abbrev/, $range);
 }
 
+# --is-ancestor requires git 1.8.0+
 sub is_ancestor ($$$) {
         my ($git, $cur, $tip) = @_;
         return 0 unless $git->check($cur);