Merge branch 'jc/show-sig'

* jc/show-sig:
  log --show-signature: reword the common two-head merge case
  log-tree: show mergetag in log --show-signature output
  log-tree.c: small refactor in show_signature()
  commit --amend -S: strip existing gpgsig headers
  verify_signed_buffer: fix stale comment
  gpg-interface: allow use of a custom GPG binary
  pretty: %G[?GS] placeholders
  test "commit -S" and "log --show-signature"
  log: --show-signature
  commit: teach --gpg-sign option

Conflicts:
	builtin/commit-tree.c
	builtin/commit.c
	builtin/merge.c
	notes-cache.c
	pretty.c

notes-merge.c

@@ -551,7 +551,7 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 		/* else: t->ref points to nothing, assume root/orphan commit */
 	}
 
-	if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL))
+	if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL, NULL))
 		die("Failed to commit notes tree to database");
 }