bitcoind: process -help/-version before touching the datadir

[kwsantiago]

Follow-up to #329, where @luke-jr asked about the comment in ProcessInitCommands() claiming help and version are processed "before taking care about datadir", when in fact ParseArgs() calls common::InitConfig() first.

InitConfig() creates the datadir and its wallets/ subdirectory, stats bitcoin.conf, and writes settings.json. So bitcoind --help and bitcoind --version both create $HOME/.bitcoin, and fail outright if it exists but is not traversable (issue #304).

Move the InitConfig() call after ProcessInitCommands(), so the comment becomes true. This is the ordering bitcoin-cli already uses: ParseParameters(), then help/version, then config.

Testing

Built with clang and compared against a pre-patch build of the same tree.

Scenario	Before	After	bitcoin-cli
fresh $HOME, --version / --help	creates .bitcoin/, wallets/, settings.json	nothing created	nothing created
chmod 444 ~/.bitcoin, --version / --help (#304)	Permission denied, exit 1	exit 0	exit 0
--help / --version output		byte-identical
--help foo (loose token)	error, exit 1	unchanged
unparseable bitcoin.conf, normal startup	error, exit 1	unchanged
-datadir=/nonexistent, normal startup	error, exit 1	unchanged

Because the config file is no longer read before help/version, three things change, all of them matching bitcoin-cli's existing behavior:

Scenario	Before	After	bitcoin-cli
help-debug=1 in bitcoin.conf, --help	expands help output	no effect	no effect
-conf=/nonexistent.conf -version	error, exit 1	prints version, exit 0	prints version, exit 0
-datadir=/nonexistent -version / -help	error, exit 1	prints output, exit 0	prints output, exit 0

-help-debug on the command line still works, and both -conf and -datadir are still validated on a normal startup.

feature_help.py, feature_config_args.py, feature_settings.py and feature_init.py pass.

[kwsantiago]

Rebased onto v29.0 as a daggy fix and force-pushed.

[pdath]

ACK 0bed563.

I reviewed the changes to src/bitcoind.cpp, and found them to be simple, low risk, and as described.

Code Rabbit reviewed the change and found no issues.

I tested using the following commands on Ubuntu 24.04 running on ARMv8-A (64-bit) and gcc to verify the the original issue #304 is resolved.

git clone https://github.com/bitcoinknots/bitcoin.git pr341
cd pr341
git fetch origin pull/341/head:pr341
git switch pr341

cmake -B build -DCMAKE_BUILD_TYPE=Release
nice cmake --build build --target bitcoind -j $(nproc)

chmod 444 ~/.bitcoin
./contrib/devtools/gen-bitcoin-conf.sh

And then verified that the following file was created and contained the expected content:

./share/examples/bitcoin.conf