A bit late to the party, but I just tried #12653 and noticed some non-intuitive behavior (on macOS), that's probably worth explaining release notes and help.

Before this new feature I kept the entire datadir on an SSD drive, so I launch with: `bitcoind -datadir=/Volumes/SSD/Bitcoin`.

Initially I naively moved `/Volumes/SSD/Bitcoin/blocks` to `/Users/bitcoin/blocks` and added a line to `/Volumes/SSD/Bitcoin/bitcoin.conf`: `blocksdir=/Users/bitcoin/blocks`.

I then realized that I shouldn't have moved the `index` subdirectory, so I moved that back to `/Volumes/SSD/Bitcoin/blocks/index`. Having an empty `blocks` dir with just and `index` subdir is a bit weird. Perhaps after @jimpo's #11857 is merged, we could just move / assume all indexes to be there (if `-blocksdir` is set)?

Worse, it created a directory `/Users/bitcoin/blocks/blocks`, which seems like a bug. I had to set `blocksdir=/Users/bitcoin` instead.
nConnectTimeout = gArgs.GetArg("-timeout", DEFAULT_CONNECT_TIMEOUT);
    if (nConnectTimeout <= 0)
        nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
    if (gArgs.IsArgSet("-minrelaytxfee")) {
        CAmount n = 0;
        if (!ParseMoney(gArgs.GetArg("-minrelaytxfee", ""), n)) {
            return InitError(AmountErrMsg("minrelaytxfee", gArgs.GetArg("-minrelaytxfee", "")));
        }
        
        ::minRelayTxFee = CFeeRate(n);
    } else if (incrementalRelayFee > ::minRelayTxFee) {
        
        ::minRelayTxFee = incrementalRelayFee;
        LogPrintf("Increasing minrelaytxfee to %s to match incrementalrelayfee\n",::minRelayTxFee.ToString());
    }
    
    
    if (gArgs.IsArgSet("-blockmintxfee"))
    {
        CAmount n = 0;
        if (!ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n))
            return InitError(AmountErrMsg("blockmintxfee", gArgs.GetArg("-blockmintxfee", "")));
    }
    
    
    if (gArgs.IsArgSet("-dustrelayfee"))
    {
        CAmount n = 0;
        if (!ParseMoney(gArgs.GetArg("-dustrelayfee", ""), n))
            return InitError(AmountErrMsg("dustrelayfee", gArgs.GetArg("-dustrelayfee", "")));