Fast sync - deprecation warning (#7906)

* fast sync log warnings for deprecation

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>

* minor text change in changelog

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>

---------

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>
Co-authored-by: Fabio Di Fabio <fabio.difabio@consensys.net>

CHANGELOG.md

@@ -28,7 +28,7 @@
 - `--host-whitelist` has been deprecated in favor of `--host-allowlist` since 2020 and will be removed in a future release
 - Sunsetting features - for more context on the reasoning behind the deprecation of these features, including alternative options, read [this blog post](https://www.lfdecentralizedtrust.org/blog/sunsetting-tessera-and-simplifying-hyperledger-besu)
   - Tessera privacy
-  - Smart-contract-based permissioning
+  - Smart-contract-based (onchain) permissioning
   - Proof of Work consensus
   - Fast Sync
 

besu/src/main/java/org/hyperledger/besu/cli/BesuCommand.java

@@ -1640,6 +1640,10 @@ public class BesuCommand implements DefaultCommandValues, Runnable {
             "--p2p-port",
             "--remote-connections-max-percentage"));
 
+    if (SyncMode.FAST == syncMode) {
+      logger.warn("FAST sync is deprecated. Recommend using SNAP sync instead.");
+    }
+
     if (SyncMode.isFullSync(getDefaultSyncModeIfNotSet())
         && isOptionSet(commandLine, "--sync-min-peers")) {
       logger.warn("--sync-min-peers is ignored in FULL sync-mode");

besu/src/main/java/org/hyperledger/besu/cli/ConfigurationOverviewBuilder.java

@@ -349,7 +349,8 @@ public class ConfigurationOverviewBuilder {
     }
 
     if (syncMode != null) {
-      lines.add("Sync mode: " + syncMode);
+      lines.add(
+          "Sync mode: " + syncMode + (syncMode.equalsIgnoreCase("FAST") ? " (Deprecated)" : ""));
     }
 
     if (syncMinPeers != null) {