BTCP-Rebase/doc/release-notes.md

(note: this is a temporary file, to be added-to by anybody, and moved to
release-notes at release time)

Bitcoin Core version *version* is now available from:

  <https://bitcoincore.org/bin/bitcoin-core-*version*/>

This is a new major version release, including new features, various bugfixes
and performance improvements, as well as updated translations.

Please report bugs using the issue tracker at GitHub:

  <https://github.com/bitcoin/bitcoin/issues>

To receive security and update notifications, please subscribe to:

  <https://bitcoincore.org/en/list/announcements/join/>

How to Upgrade
==============

If you are running an older version, shut it down. Wait until it has completely
shut down (which might take a few minutes for older versions), then run the
installer (on Windows) or just copy over `/Applications/Bitcoin-Qt` (on Mac)
or `bitcoind`/`bitcoin-qt` (on Linux).

The first time you run version 0.15.0, your chainstate database will be converted to a
new format, which will take anywhere from a few minutes to half an hour,
depending on the speed of your machine.

Note that the block database format also changed in version 0.8.0 and there is no
automatic upgrade code from before version 0.8 to version 0.15.0. Upgrading
directly from 0.7.x and earlier without redownloading the blockchain is not supported.
However, as usual, old wallet versions are still supported.

Downgrading warning
-------------------

The chainstate database for this release is not compatible with previous
releases, so if you run 0.15 and then decide to switch back to any
older version, you will need to run the old release with the `-reindex-chainstate`
option to rebuild the chainstate data structures in the old format.

If your node has pruning enabled, this will entail re-downloading and
processing the entire blockchain.

Compatibility
==============

Bitcoin Core is extensively tested on multiple operating systems using
the Linux kernel, macOS 10.8+, and Windows 7 and newer (Windows XP is not supported).

Bitcoin Core should also work on most other Unix-like systems but is not
frequently tested on them.

Notable changes
===============

GUI changes
-----------

- Block storage can be limited under Preferences, in the Main tab. Undoing this setting requires downloading the full blockchain again. This mode is incompatible with -txindex and -rescan.

RPC changes
------------

### Low-level changes

- The `createrawtransaction` RPC will now accept an array or dictionary (kept for compatibility) for the `outputs` parameter. This means the order of transaction outputs can be specified by the client.
- The `fundrawtransaction` RPC will reject the previously deprecated `reserveChangeKey` option.
- `sendmany` now shuffles outputs to improve privacy, so any previously expected behavior with regards to output ordering can no longer be relied upon.
- The new RPC `testmempoolaccept` can be used to test acceptance of a transaction to the mempool without adding it.
- JSON transaction decomposition now includes a `weight` field which provides
  the transaction's exact weight. This is included in REST /rest/tx/ and
  /rest/block/ endpoints when in json mode. This is also included in `getblock`
  (with verbosity=2), `listsinceblock`, `listtransactions`, and
  `getrawtransaction` RPC commands.
- New `fees` field introduced in `getrawmempool`, `getmempoolancestors`, `getmempooldescendants` and
   `getmempoolentry` when verbosity is set to `true` with sub-fields `ancestor`, `base`, `modified`
   and `descendant` denominated in BTC. This new field deprecates previous fee fields, such as
   `fee`, `modifiedfee`, `ancestorfee` and `descendantfee`.

External wallet files
---------------------

The `-wallet=<path>` option now accepts full paths instead of requiring wallets
to be located in the -walletdir directory.

Newly created wallet format
---------------------------

If `-wallet=<path>` is specified with a path that does not exist, it will now
create a wallet directory at the specified location (containing a wallet.dat
data file, a db.log file, and database/log.?????????? files) instead of just
creating a data file at the path and storing log files in the parent
directory. This should make backing up wallets more straightforward than
before because the specified wallet path can just be directly archived without
having to look in the parent directory for transaction log files.

For backwards compatibility, wallet paths that are names of existing data files
in the `-walletdir` directory will continue to be accepted and interpreted the
same as before.

Low-level RPC changes
---------------------

- When bitcoin is not started with any `-wallet=<path>` options, the name of
  the default wallet returned by `getwalletinfo` and `listwallets` RPCs is
  now the empty string `""` instead of `"wallet.dat"`. If bitcoin is started
  with any `-wallet=<path>` options, there is no change in behavior, and the
  name of any wallet is just its `<path>` string.
- Passing an empty string (`""`) as the `address_type` parameter to
  `getnewaddress`, `getrawchangeaddress`, `addmultisigaddress`,
  `fundrawtransaction` RPCs is now an error. Previously, this would fall back
  to using the default address type. It is still possible to pass null or leave
  the parameter unset to use the default address type.

- Bare multisig outputs to our keys are no longer automatically treated as
  incoming payments. As this feature was only available for multisig outputs for
  which you had all private keys in your wallet, there was generally no use for
  them compared to single-key schemes. Furthermore, no address format for such
  outputs is defined, and wallet software can't easily send to it. These outputs
  will no longer show up in `listtransactions`, `listunspent`, or contribute to
  your balance, unless they are explicitly watched (using `importaddress` or
  `importmulti` with hex script argument). `signrawtransaction*` also still
  works for them.

### Logging

- The log timestamp format is now ISO 8601 (e.g. "2018-02-28T12:34:56Z").

Miner block size removed
------------------------

The `-blockmaxsize` option for miners to limit their blocks' sizes was
deprecated in V0.15.1, and has now been removed. Miners should use the
`-blockmaxweight` option if they want to limit the weight of their blocks'
weights.

Python Support
--------------

Support for Python 2 has been discontinued for all test files and tools.

Credits
=======

Thanks to everyone who directly contributed to this release:


As well as everyone that helped translating on [Transifex](https://www.transifex.com/projects/p/bitcoin/).