Merge bitcoin#1946: Testing framework, adding mocktime startup arg.

bde4f4b Adding mocktime startup arg. (furszy)

Pull request description:

  Startup option to initialize the node with mocktime set (regression testing only).
  Hidden issue: the functional testing framework is already trying to use it without any luck as the startup option doesn't exist. (`TestNode` class, line 70).

  Extra notes, this fixes bitcoin#1916 tier two functional testing sync issues.

ACKs for top commit:
  random-zebra:
    great find! utACK bde4f4b
  Fuzzbawls:
    utACK bde4f4b

Tree-SHA512: bbf6b116edf0cbd0fb754878e261c6fbaa7aff1e6b0e74894bf2ffa780cfdf7581c30e8af736283a12597e6e60c37694c9adbf388fefb56a38bfc5245632e412

src/init.cpp

@@ -505,6 +505,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-logtimestamps", strprintf(_("Prepend debug output with timestamp (default: %u)"), DEFAULT_LOGTIMESTAMPS));
     strUsage += HelpMessageOpt("-logtimemicros", strprintf("Add microsecond precision to debug timestamps (default: %u)", DEFAULT_LOGTIMEMICROS));
     if (showDebug) {
+        strUsage += HelpMessageOpt("-mocktime=<n>", "Replace actual time with <n> seconds since epoch (default: 0)");
         strUsage += HelpMessageOpt("-limitfreerelay=<n>", strprintf(_("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default:%u)"), DEFAULT_LIMITFREERELAY));
         strUsage += HelpMessageOpt("-relaypriority", strprintf(_("Require high priority for relaying free or low-fee transactions (default:%u)"), DEFAULT_RELAYPRIORITY));
         strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf(_("Limit size of signature cache to <n> MiB (default: %u)"), DEFAULT_MAX_SIG_CACHE_SIZE));
@@ -1119,6 +1120,11 @@ bool AppInit2()
     fIsBareMultisigStd = gArgs.GetBoolArg("-permitbaremultisig", DEFAULT_PERMIT_BAREMULTISIG);
     nMaxDatacarrierBytes = gArgs.GetArg("-datacarriersize", nMaxDatacarrierBytes);
 
+    // Option to startup with mocktime set (used for regression testing):
+    if (Params().IsRegTestNet()) {
+        SetMockTime(gArgs.GetArg("-mocktime", 0)); // SetMockTime(0) is a no-op
+    }
+
     ServiceFlags nLocalServices = NODE_NETWORK;
     ServiceFlags nRelevantServices = NODE_NETWORK;