Merge pulls #1105 and #1118

- #1105: Dev Docs: drop mention of endianness in hash byte order
- #1118: Dev Docs: update v4 blocks text; mention version bits

_includes/devdoc/bitcoin-core/api-intro.md

@@ -12,23 +12,23 @@ http://opensource.org/licenses/MIT.
 
 {% autocrossref %}
 
-Bitcoin Core RPCs accept and return hashes in the reverse of their
+Bitcoin Core RPCs accept and return the byte-wise reverse of computed
-normal byte order. For example, the Unix `sha256sum` command would display the
+SHA-256 hash values. For example, the Unix `sha256sum` command displays the
-SHA256(SHA256()) hash of mainnet block 300,000's header as the
+SHA256(SHA256()) hash of mainnet block 300,000's header as:
-following string:
 
+    > /bin/echo -n '020000007ef055e1674d2e6551dba41cd214debbee34aeb544c7ec670000000000000000d3998963f80c5bab43fe8c26228e98d030edf4dcbe48a666f5c39e2d7a885c9102c86d536c890019593a470d' | xxd -r -p | sha256sum -b | xxd -r -p | sha256sum -b
     5472ac8b1187bfcf91d6d218bbda1eb2405d7c55f1f8cc820000000000000000
 
-The string above is also how the hash appears in the
+The result above is also how the hash appears in the
 previous-header-hash part of block 300,001's header:
 
 <pre>02000000<b>5472ac8b1187bfcf91d6d218bbda1eb2405d7c55f1f8cc82000\
 0000000000000</b>ab0aaa377ca3f49b1545e2ae6b0667a08f42e72d8c24ae\
 237140e28f14f3bb7c6bcc6d536c890019edd83ccf</pre>
 
-However Bitcoin RPCs use the reverse byte order for hashes, so if you
+However, Bitcoin Core's RPCs use the byte-wise reverse for hashes, so if you
 want to get information about block 300,000 using the `getblock` RPC,
-you need to reverse the byte order:
+you need to reverse the requested hash:
 
     > bitcoin-cli getblock \
       000000000000000082ccf8f1557c5d40b21edabb18d2d691cfbf87118bac7254
@@ -37,26 +37,19 @@ you need to reverse the byte order:
 data, which is why the reversed string looks somewhat mangled.)
 
 The rationale for the reversal is unknown, but it likely stems from
-Bitcoin's use of hash digests (which are byte arrays in C++) as integers
+Bitcoin Core's use of hashes (which are byte arrays in C++) as integers
 for the purpose of determining whether the hash is below the network
 target. Whatever the reason for reversing header hashes, the reversal
 also extends to other hashes used in RPCs, such as TXIDs and merkle
 roots.
 
-Off-site documentation such as the Bitcoin Wiki tends to use the terms
-big endian and little endian as shown in the table below, but they
-aren't always consistent. Worse, these two different ways of
-representing a hash digest can confuse anyone who looks at the Bitcoin
-Core source code and finds a so-called "big endian" value being stored
-in a little-endian data type.
-
 As header hashes and TXIDs are widely used as global identifiers in
 other Bitcoin software, this reversal of hashes has become the standard
 way to refer to certain objects. The table below should make clear where
 each byte order is used.
 
 |---------------+---------------------|-----------------|
-| Data | Internal Byte Order ("Big Endian") | RPC Byte Order ("Little Endian") |
+| Data | Internal Byte Order | RPC Byte Order |
 |---------------|---------------------|-----------------|
 | Example: SHA256(SHA256(0x00))  | Hash: 1406...539a         | Hash: 9a53...0614     |
 |---------------|---------------------|-----------------|

_includes/devdoc/ref_block_chain.md

@@ -72,17 +72,21 @@ fe9f0864 ........................... Nonce
   encoding had previously been non-standard since Bitcoin Core 0.8.0
   (February 2012).
 
-* **Version 4** blocks will likely be introduced in the near-future as
+* **Version 4** blocks will likely be introduced in the near future as
-  specified in draft BIP62. Possible changes include:
+  specified in BIP65.   These blocks will support the new
+  `OP_CHECKLOCKTIMEVERIFY` opcode described in that BIP.
 
-    * Reject version 4 blocks that include any version 2 transactions
+The mechanism used for the version 2, 3, and 4 upgrades is commonly
-      that don't adhere to any of the version 2 transaction rules.
+called IsSuperMajority() after the function added to Bitcoin Core to
-      These rules are not yet described in this documentation; see
+manage those soft forking changes. See BIP34 for a full description of
-      BIP62 for details.
+this method.
 
-    * A soft fork rollout of version 4 blocks identical to the rollout
+As of this writing, a newer method called *version bits* is being designed
-      used for version 3 blocks (described briefly in BIP62 and in more
+to manage future soft forking changes, although it's not known whether
-      detail in BIP34).
+version 4 will be the last soft fork to use the IsSuperMajority()
+function. Draft BIP9 describes the version bits design as of this
+writing, although it is still being actively edited and may
+substantially change while in the draft state.
 
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