Merge #13662: Explain when reindex-chainstate can be used instead of reindex

Summary:
65a449f8e3 Explain when reindex-chainstate can be used instead of reindex (Sjors Provoost)

Pull request description:

  Save users from having to Google this: https://bitcoin.stackexchange.com/a/60711

Tree-SHA512: 3128565d037c77265a2ecf3bce137b8d27740f513802a4e683be06f21a75b82ee6cc22eb903181c4f438a2990cb682ce1d076f4d3af33d5aaa79b783a9f664b1

Backport of Core PR13662
bitcoin/bitcoin#13662

Test Plan:
  make check
  ./bitcoind --help
Verify help test for `-reindex-chainstate`.

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: Fabien, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D4741

Author: MarcoFalke

src/init.cpp

@@ -512,8 +512,10 @@ void SetupServerArgs() {
                   MIN_DISK_SPACE_FOR_BLOCK_FILES / 1024 / 1024),
         false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-reindex-chainstate",
-                 "Rebuild chain state from the currently indexed blocks", false,
-                 OptionsCategory::OPTIONS);
+                 "Rebuild chain state from the currently indexed blocks. When "
+                 "in pruning mode or if blocks on disk might be corrupted, use "
+                 "full -reindex instead.",
+                 false, OptionsCategory::OPTIONS);
     gArgs.AddArg(
         "-reindex",
         "Rebuild chain state and block index from the blk*.dat files on disk",