[doc] Include txindex changes in the release notes.

Author: Jim Posen

doc/files.md

@@ -10,6 +10,7 @@
 * db.log: wallet database log file; moved to wallets/ directory on new installs since 0.16.0
 * debug.log: contains debug information and general logging generated by bitcoind or bitcoin-qt
 * fee_estimates.dat: stores statistics used to estimate minimum transaction fees and priorities required for confirmation; since 0.10.0
+* indexes/txindex/*: optional transaction index database (LevelDB); since 0.17.0
 * mempool.dat: dump of the mempool's transactions; since 0.14.0.
 * peers.dat: peer IP address database (custom format); since 0.7.0
 * wallet.dat: personal wallet (BDB) with keys and transactions; moved to wallets/ directory on new installs since 0.16.0

doc/release-notes-pr13033.md

@@ -0,0 +1,11 @@
+Transaction index changes
+-------------------------
+
+The transaction index is now built separately from the main node procedure,
+meaning the `-txindex` flag can be toggled without a full reindex. If bitcoind
+is run with `-txindex` on a node that is already partially or fully synced
+without one, the transaction index will be built in the background and become
+available once caught up. When switching from running `-txindex` to running
+without the flag, the transaction index database will *not* be deleted
+automatically, meaning it could be turned back on at a later time without a full
+resync.