Fix test failures on Ubuntu

Refer to PR book#22 and book#23 for details

t/20-simple.t

@@ -85,6 +85,12 @@ SKIP: {
     skip "this test does not work with msysgit on Win32", 2
         if $^O eq 'MSWin32';
 
+    # Thanks to @adelton and @gregora for the heads-up regarding change in behavior of git var GIT_EDITOR
+    # Refer to:  https://github.com/book/Git-Repository/pull/23
+    # for more information.
+    skip "'git var GIT_EDITOR' behaviour was changed in git 2.40.0, and we have $version", 2
+         if Git::Repository->version_ge('2.40.0');
+
     ok( !eval { $r->run( var => 'GIT_EDITOR' ); 1; }, 'git var GIT_EDITOR' );
     like(
         $@,

t/21-submodule.t

@@ -43,7 +43,18 @@ $s->run( checkout => 'master', { quiet => 1 } );
 
 # now test adding a submodule
 my $r = test_repository(@init);
+
+# The "-c" option was introduced in 1.7.2,
+# but protocol.<name>.allow was added in 2.12.0,
+# and from that version protocol.file.allow defaulted to "always",
+# from 2.38.1 however, protocol.file.allow default behavior changed to "user"
+# For versions between 1.7.2 and 2.12.0, giving "-c protocol.file.allow=always" option
+# is simply a no-op
+# Thanks to @ap for the heads-up: Refer to:
+#   https://github.com/book/Git-Repository/pull/22#issuecomment-1404255657
+# for more information.
 $r->run(
+    ( Git::Repository->version_ge('1.7.2') ? ('-c', 'protocol.file.allow=always') : ()),
     submodule => add => $s->work_tree => 'sub',
     { env => { GIT_WORK_TREE => undef } }
 );