allow git-bundle to create bottomless bundle

While "git bundle" was a useful way to sneakernet incremental
changes, we did not allow:

	$ git bundle create v2.6.20.bndl v2.6.20

to create a bundle that contains the whole history to a
well-known good revision.  Such a bundle can be mirrored
everywhere, and people can prime their repository with it to
reduce the load on the repository that serves near the tip of
the development.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5510-fetch.sh

@@ -145,4 +145,12 @@ test_expect_success 'bundle does not prerequisite objects' '
 	test 4 = $(git verify-pack -v bundle.pack | wc -l)
 '
 
+test_expect_success 'bundle should be able to create a full history' '
+
+	cd "$D" &&
+	git tag -a -m '1.0' v1.0 master &&
+	git bundle create bundle4 v1.0
+
+'
+
 test_done