t9500: ensure that algorithm info is preserved in config
When we use a hash algorithm other than SHA-1, it's important to
preserve the hash-related values in the config file, but this test
overwrites the config file with a new one. Ensure we copy these values
properly from the old config to the new one so that the repository can
be read if it's using SHA-256.
Note that if there is no extensions.objectFormat value set, git config
will return unsuccessfully if we try to read it; since this is not an
error for us, use test_might_fail.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>