Merge bitcoin/bitcoin#15936: interfaces: Expose settings.json methods to GUI

f9fdcec7e932843a91ddf7f377e00bd2a6efb82a settings: Add resetSettings() method (Ryan Ofsky)
77fabffef4ea840ee15c97061048fe8443d74658 init: Remove Shutdown() node.args reset (Ryan Ofsky)
0e55bc6e7fe439404dc56093a0949395dae51e6b settings: Add update/getPersistent/isIgnored methods (Ryan Ofsky)

Pull request description:

  Add `interfaces::Node` `updateSetting`, `forceSetting`, `resetSettings`, `isSettingIgnored`, and `getPersistentSetting` methods so GUI is able to manipulate `settings.json` file and use and modify node settings.

  (Originally this PR also contained GUI changes to unify bitcoin-qt and bitcoind persistent settings and call these methods, but the GUI commits have been dropped from this PR and moved to bitcoin-core/gui/pull/602)

ACKs for top commit:
  vasild:
    ACK f9fdcec7e932843a91ddf7f377e00bd2a6efb82a
  hebasto:
    re-ACK f9fdcec7e932843a91ddf7f377e00bd2a6efb82a, only a function renamed since my recent [review](https://github.com/bitcoin/bitcoin/pull/15936#pullrequestreview-979324357).

Tree-SHA512: 4cac853ee29be96d2ff38404165b9dfb7c622b2a9c99a15979596f3484ffde0da3d9c9c372677dff5119ca7cffa6383d81037fd9889a29cc9285882a8dc0c268

1 files changed, 24 insertions, 5 deletions

diff --git a/src/interfaces/node.h b/src/interfaces/node.h
index c4dc303dd5..2c31e12ada 100644
--- a/src/interfaces/node.h
+++ b/src/interfaces/node.h
@@ -5,12 +5,13 @@
 #ifndef BITCOIN_INTERFACES_NODE_H
 #define BITCOIN_INTERFACES_NODE_H
 
-#include <consensus/amount.h>
-#include <net.h>        // For NodeId
-#include <net_types.h>  // For banmap_t
-#include <netaddress.h> // For Network
-#include <netbase.h>    // For ConnectionDirection
+#include <consensus/amount.h>          // For CAmount
+#include <net.h>                       // For NodeId
+#include <net_types.h>                 // For banmap_t
+#include <netaddress.h>                // For Network
+#include <netbase.h>                   // For ConnectionDirection
 #include <support/allocators/secure.h> // For SecureString
+#include <util/settings.h>             // For util::SettingsValue
 #include <util/translation.h>
 
 #include <functional>
@@ -97,6 +98,24 @@ public:
     //! Return whether shutdown was requested.
     virtual bool shutdownRequested() = 0;
 
+    //! Return whether a particular setting in <datadir>/settings.json is or
+    //! would be ignored because it is also specified in the command line.
+    virtual bool isSettingIgnored(const std::string& name) = 0;
+
+    //! Return setting value from <datadir>/settings.json or bitcoin.conf.
+    virtual util::SettingsValue getPersistentSetting(const std::string& name) = 0;
+
+    //! Update a setting in <datadir>/settings.json.
+    virtual void updateRwSetting(const std::string& name, const util::SettingsValue& value) = 0;
+
+    //! Force a setting value to be applied, overriding any other configuration
+    //! source, but not being persisted.
+    virtual void forceSetting(const std::string& name, const util::SettingsValue& value) = 0;
+
+    //! Clear all settings in <datadir>/settings.json and store a backup of
+    //! previous settings in <datadir>/settings.json.bak.
+    virtual void resetSettings() = 0;
+
     //! Map port.
     virtual void mapPort(bool use_upnp, bool use_natpmp) = 0;