Refactor GetMinimumFee to give option of providing targetFee

src/wallet/wallet.cpp

@@ -2790,8 +2790,13 @@ CAmount CWallet::GetRequiredFee(unsigned int nTxBytes)
 
 CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool)
 {
-    // payTxFee is user-set "I want to pay this much"
-    CAmount nFeeNeeded = payTxFee.GetFee(nTxBytes);
+    // payTxFee is the user-set global for desired feerate
+    return GetMinimumFee(nTxBytes, nConfirmTarget, pool, payTxFee.GetFee(nTxBytes));
+}
+
+CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool, CAmount targetFee)
+{
+    CAmount nFeeNeeded = targetFee;
     // User didn't set: use -txconfirmtarget to estimate...
     if (nFeeNeeded == 0) {
         int estimateFoundTarget = nConfirmTarget;

src/wallet/wallet.h

@@ -802,6 +802,11 @@ public:
      * and the required fee
      */
     static CAmount GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool);
+    /**
+     * Estimate the minimum fee considering required fee and targetFee or if 0
+     * then fee estimation for nConfirmTarget
+     */
+    static CAmount GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarget, const CTxMemPool& pool, CAmount targetFee);
     /**
      * Return the minimum required fee taking into account the
      * floating relay fee and user set minimum transaction fee