With the new HD wallet code, importing wallets by xpub is now a possibility.

This would facilitate the creation of watch-only wallets. The current process, as I understand it, includes:

• Create a new wallet.dat (with createwallet or on first-run)
• Use dumpwallet to create a file with the extended private masterkey
• Delete the wallet
• Recreate the wallet from its xprv with createwallet "name" true, so it is watch-only

This doesn't consider the use case where an offline external client generates the xprv and xpub

We should be allowed to import an xpub:

• At the root
• At a given derivation path