doc: Various validation doc fixups

* Rename RewindBlockIndex -> NeedsRedownload (follow-up to commit
  d831e71)
* Fix typos
* Inline comments about faking chain data to avoid duplicating them

Author: MarcoFalke

src/chain.h

@@ -182,7 +182,7 @@ class CBlockIndex
     //!
     //! Note: this value is modified to show BLOCK_OPT_WITNESS during UTXO snapshot
     //! load to avoid the block index being spuriously rewound.
-    //! @sa RewindBlockIndex
+    //! @sa NeedsRedownload
     //! @sa ActivateSnapshot
     uint32_t nStatus{0};
 

src/validation.cpp

@@ -1401,8 +1401,9 @@ void CChainState::InvalidChainFound(CBlockIndex* pindexNew)
 }
 
 // Same as InvalidChainFound, above, except not called directly from InvalidateBlock,
-// which does its own setBlockIndexCandidates manageent.
-void CChainState::InvalidBlockFound(CBlockIndex *pindex, const BlockValidationState &state) {
+// which does its own setBlockIndexCandidates management.
+void CChainState::InvalidBlockFound(CBlockIndex* pindex, const BlockValidationState& state)
+{
     if (state.GetResult() != BlockValidationResult::BLOCK_MUTATED) {
         pindex->nStatus |= BLOCK_FAILED_VALID;
         m_blockman.m_failed_blocks.insert(pindex);
@@ -1819,8 +1820,8 @@ bool CChainState::ConnectBlock(const CBlock& block, BlockValidationState& state,
     // may have let in a block that violates the rule prior to updating the
     // software, and we would NOT be enforcing the rule here. Fully solving
     // upgrade from one software version to the next after a consensus rule
-    // change is potentially tricky and issue-specific (see RewindBlockIndex()
-    // for one general approach that was used for BIP 141 deployment).
+    // change is potentially tricky and issue-specific (see NeedsRedownload()
+    // for one approach that was used for BIP 141 deployment).
     // Also, currently the rule against blocks more than 2 hours in the future
     // is enforced in ContextualCheckBlockHeader(); we wouldn't want to
     // re-enforce that rule here (at least until we make it impossible for
@@ -5079,24 +5080,20 @@ bool ChainstateManager::PopulateAndValidateSnapshot(
     LOCK(::cs_main);
 
     // Fake various pieces of CBlockIndex state:
-    //
-    //   - nChainTx: so that we accurately report IBD-to-tip progress
-    //   - nTx: so that LoadBlockIndex() loads assumed-valid CBlockIndex entries
-    //       (among other things)
-    //   - nStatus & BLOCK_OPT_WITNESS: so that RewindBlockIndex() doesn't zealously
-    //       unwind the assumed-valid chain.
-    //
     CBlockIndex* index = nullptr;
     for (int i = 0; i <= snapshot_chainstate.m_chain.Height(); ++i) {
         index = snapshot_chainstate.m_chain[i];
 
+        // Fake nTx so that LoadBlockIndex() loads assumed-valid CBlockIndex
+        // entries (among other things)
         if (!index->nTx) {
             index->nTx = 1;
         }
+        // Fake nChainTx so that GuessVerificationProgress reports accurately
         index->nChainTx = index->pprev ? index->pprev->nChainTx + index->nTx : 1;
 
-        // We need to fake this flag so that CChainState::RewindBlockIndex()
-        // won't try to rewind the entire assumed-valid chain on startup.
+        // Fake BLOCK_OPT_WITNESS so that CChainState::NeedsRedownload()
+        // won't ask to rewind the entire assumed-valid chain on startup.
         if (index->pprev && ::IsWitnessEnabled(index->pprev, ::Params().GetConsensus())) {
             index->nStatus |= BLOCK_OPT_WITNESS;
         }

src/validation.h

@@ -555,7 +555,7 @@ enum class CoinsCacheSizeState
  *
  * Anything that is contingent on the current tip of the chain is stored here,
  * whereas block information and metadata independent of the current tip is
- * kept in `BlockMetadataManager`.
+ * kept in `BlockManager`.
  */
 class CChainState
 {