allow txindex to be removed and add a reindex dialog

- adds a reindex dialog for Bitcoin-Qt to change -txindex without the need
  to supply -reindex
- now also does a -reindex, when removing the -txindex switch

src/init.cpp

@@ -744,6 +744,12 @@ bool AppInit2(boost::thread_group& threadGroup)
                 if (!mapBlockIndex.empty() && pindexGenesisBlock == NULL)
                     return InitError(_("Incorrect or no genesis block found. Wrong datadir for network?"));
 
+                // Check for changed -txindex state (only necessary if we are not reindexing anyway)
+                if (!fReindex && fTxIndex != GetBoolArg("-txindex", false)) {
+                    strLoadError = _("You need to rebuild the database using -reindex to change -txindex");
+                    break;
+                }
+
                 // Initialize the block index (no-op if non-empty database was already loaded)
                 if (!InitBlockIndex()) {
                     strLoadError = _("Error initializing block database");
@@ -767,7 +773,7 @@ bool AppInit2(boost::thread_group& threadGroup)
             // first suggest a reindex
             if (!fReset) {
                 bool fRet = uiInterface.ThreadSafeMessageBox(
-                    strLoadError + ".\n" + _("Do you want to rebuild the block database now?"),
+                    strLoadError + ".\n\n" + _("Do you want to rebuild the block database now?"),
                     "", CClientUIInterface::MSG_ERROR | CClientUIInterface::BTN_ABORT);
                 if (fRet) {
                     fReindex = true;
@@ -781,9 +787,6 @@ bool AppInit2(boost::thread_group& threadGroup)
         }
     }
 
-    if (mapArgs.count("-txindex") && fTxIndex != GetBoolArg("-txindex", false))
-        return InitError(_("You need to rebuild the databases using -reindex to change -txindex"));
-
     // as LoadBlockIndex can take several minutes, it's possible the user
     // requested to kill bitcoin-qt during the last operation. If so, exit.
     // As the program has not fully started yet, Shutdown() is possibly overkill.

src/qt/bitcoinstrings.cpp

@@ -205,6 +205,6 @@ QT_TRANSLATE_NOOP("bitcoin-core", "Verifying wallet..."),
 QT_TRANSLATE_NOOP("bitcoin-core", "Wallet needed to be rewritten: restart Bitcoin to complete"),
 QT_TRANSLATE_NOOP("bitcoin-core", "Warning"),
 QT_TRANSLATE_NOOP("bitcoin-core", "Warning: This version is obsolete, upgrade required!"),
-QT_TRANSLATE_NOOP("bitcoin-core", "You need to rebuild the databases using -reindex to change -txindex"),
+QT_TRANSLATE_NOOP("bitcoin-core", "You need to rebuild the database using -reindex to change -txindex"),
 QT_TRANSLATE_NOOP("bitcoin-core", "wallet.dat corrupt, salvage failed"),
 };