Display descriptors for BTC Taproot accounts

[Hannsek]

Discussed here.

[prusnak]

Python code for calculating descriptors is here:

trezor-firmware/python/src/trezorlib/cli/btc.py

Lines 279 to 336 in f4d3a74

	def _get_descriptor(
	client: "TrezorClient",
	coin: Optional[str],
	account: int,
	purpose: Optional[int],
	script_type: Optional[messages.InputScriptType],
	show_display: bool,
	) -> str:
	if purpose is None:
	if script_type is None:
	script_type = messages.InputScriptType.SPENDADDRESS
	purpose = SCRIPT_TYPE_TO_BIP_PURPOSES[script_type][0]
	elif script_type is None:
	script_type = BIP_PURPOSE_TO_DEFAULT_SCRIPT_TYPE[purpose]
	else:
	if purpose not in SCRIPT_TYPE_TO_BIP_PURPOSES[script_type]:
	raise ValueError("Invalid script type for account type")
	if script_type == messages.InputScriptType.SPENDADDRESS:
	fmt = "pkh({})"
	elif script_type == messages.InputScriptType.SPENDP2SHWITNESS:
	fmt = "sh(wpkh({}))"
	elif script_type == messages.InputScriptType.SPENDWITNESS:
	fmt = "wpkh({})"
	elif script_type == messages.InputScriptType.SPENDTAPROOT:
	fmt = "tr({})"
	else:
	raise ValueError("Unsupported script type")
	coin = coin or DEFAULT_COIN
	if coin == "Bitcoin":
	coin_type = 0
	elif coin == "Testnet" or coin == "Regtest":
	coin_type = 1
	else:
	raise ValueError("Unsupported coin")
	path = f"m/{purpose}h/{coin_type}h/{account}h"
	if purpose == PURPOSE_SLIP25:
	if script_type == messages.InputScriptType.SPENDTAPROOT:
	path += "/1h"
	else:
	raise ValueError("Unsupported SLIP25 script type")
	n = tools.parse_path(path)
	pub = btc.get_public_node(
	client,
	n,
	show_display=show_display,
	coin_name=coin,
	script_type=script_type,
	ignore_xpub_magic=True,
	unlock_path=get_unlock_path(n),
	)
	fingerprint = pub.root_fingerprint if pub.root_fingerprint is not None else 0
	descriptor = f"[{fingerprint:08x}{path[1:]}]{pub.xpub}/<0;1>/*"
	return _append_descriptor_checksum(fmt.format(descriptor))