Don't archive sessions when they are fresh.

AxolotlKit/Classes/Sessions/SessionRecord.m

@@ -86,6 +86,10 @@
 }
 
 - (void)archiveCurrentState{
+    if (self.sessionState.isFresh) {
+        OWSLogInfo(@"Skipping archive, current session state is fresh.");
+        return;
+    }
     [self promoteState:[SessionState new]];
 }
 

AxolotlKit/Classes/Sessions/SessionState.h

@@ -39,6 +39,8 @@
 @property(nonatomic)int remoteRegistrationId;
 @property(nonatomic)int localRegistrationId;
 
+@property (nonatomic, readonly) BOOL isFresh;
+
 - (NSData*)senderRatchetKey;
 - (ECKeyPair*)senderRatchetKeyPair;
 

AxolotlKit/Classes/Sessions/SessionState.m

@@ -119,6 +119,11 @@ static NSString* const kCoderPendingPrekey    = @"kCoderPendingPrekey";
     [aCoder encodeObject:self.pendingPreKey forKey:kCoderPendingPrekey];
 }
 
+- (BOOL)isFresh
+{
+    return self.remoteIdentityKey == nil && self.localIdentityKey == nil && self.sendingChain == nil && self.receivingChains.count == 0 && self.pendingPreKey == nil;
+}
+
 - (NSData*)senderRatchetKey{
     return [[self senderRatchetKeyPair] publicKey];
 }