Some embeddings of UploadPack (e.g. Gerrit Code Review) set their own
PackConfig from a server-wide configuration, overriding any JGit
defaults or settings that may exist at the local repository level.
Make a copy constructor form of PackConfig so this server-wide
configuration object can be copied and then merged with repository
specific configuration data.
Change-Id: I4463c95aeaf7d6536c3ab132dec9c50ee528d9e0 Signed-off-by: Shawn O. Pearce <spearce@spearce.org>