Introduce explicit -walletupgrade option

Do not automatically change the wallet format unless the user takes an
explicit action that implies an upgrade (encrypting, for now), or uses
-walletupgrade.

-walletupgrade optionally takes an integer argument: the client version
up to which upgrading is allowed. Without an argument, it is upgraded
to latest supported version. If an argument to -walletupgrade is
provided at the time the wallet is created, the new wallet will initially
not use features beyond that version.

Third, the current wallet version number is reported in getinfo.

src/wallet.cpp

@@ -17,7 +17,7 @@ using namespace std;
 
 std::vector<unsigned char> CWallet::GenerateNewKey()
 {
-    bool fCompressed = true; // default to compressed public keys
+    bool fCompressed = CanSupportFeature(FEATURE_COMPRPUBKEY); // default to compressed public keys if we want 0.6.0 wallets
 
     RandAddSeedPerfmon();
     CKey key;
@@ -25,7 +25,7 @@ std::vector<unsigned char> CWallet::GenerateNewKey()
 
     // Compressed public keys were introduced in version 0.6.0
     if (fCompressed)
-        SetMinVersion(59900);
+        SetMinVersion(FEATURE_COMPRPUBKEY);
 
     if (!AddKey(key))
         throw std::runtime_error("CWallet::GenerateNewKey() : AddKey failed");
@@ -148,13 +148,20 @@ public:
     )
 };
 
-bool CWallet::SetMinVersion(int nVersion, CWalletDB* pwalletdbIn)
+bool CWallet::SetMinVersion(enum WalletFeature nVersion, CWalletDB* pwalletdbIn, bool fExplicit)
 {
     if (nWalletVersion >= nVersion)
         return true;
 
+    // when doing an explicit upgrade, if we pass the max version permitted, upgrade all the way
+    if (fExplicit && nVersion > nWalletMaxVersion)
+            nVersion = FEATURE_LATEST;
+
     nWalletVersion = nVersion;
 
+    if (nVersion > nWalletMaxVersion)
+        nWalletMaxVersion = nVersion;
+
     if (fFileBacked)
     {
         CWalletDB* pwalletdb = pwalletdbIn ? pwalletdbIn : new CWalletDB(strWalletFile);
@@ -174,6 +181,17 @@ bool CWallet::SetMinVersion(int nVersion, CWalletDB* pwalletdbIn)
     return true;
 }
 
+bool CWallet::SetMaxVersion(int nVersion)
+{
+    // cannot downgrade below current version
+    if (nWalletVersion > nVersion)
+        return false;
+
+    nWalletMaxVersion = nVersion;
+
+    return true;
+}
+
 bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
 {
     if (IsCrypted())
@@ -228,7 +246,7 @@ bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
         }
 
         // Encryption was introduced in version 0.4.0
-        SetMinVersion(40000, pwalletdbEncryption);
+        SetMinVersion(FEATURE_WALLETCRYPT, pwalletdbEncryption, true);
 
         if (fFileBacked)
         {
@@ -1253,19 +1271,6 @@ int CWallet::LoadWallet(bool& fFirstRunRet)
         return nLoadWalletRet;
     fFirstRunRet = vchDefaultKey.empty();
 
-    if (!HaveKey(Hash160(vchDefaultKey)))
-    {
-        // Create new keyUser and set as default key
-        RandAddSeedPerfmon();
-
-        std::vector<unsigned char> newDefaultKey;
-        if (!GetKeyFromPool(newDefaultKey, false))
-            return DB_LOAD_FAIL;
-        SetDefaultKey(newDefaultKey);
-        if (!SetAddressBookName(CBitcoinAddress(vchDefaultKey), ""))
-            return DB_LOAD_FAIL;
-    }
-
     CreateThread(ThreadFlushWalletDB, &strWalletFile);
     return DB_LOAD_OK;
 }