git: show the version of `pygit2` with verbose version output This seems like useful info to have when debugging. I followed the precedent of hg-git, which prints something like: hggit external 0.9.0a1 (dulwich 0.19.15) We don't have a version number assigned (because it's internal), so it's just the parenthetical. Differential Revision: https://phab.mercurial-scm.org/D9436

--- a/tests/test-git-interop.t	Fri Nov 27 15:17:42 2020 -0500
+++ b/tests/test-git-interop.t	Thu Nov 26 15:09:57 2020 -0500
@@ -16,6 +16,10 @@
   >  }
 
 
+  $ hg version -v --config extensions.git= | grep '^[E ]'
+  Enabled extensions:
+    git  internal  (pygit2 *) (glob)
+
 Test auto-loading extension works:
   $ mkdir nogit
   $ cd nogit