db/Interface: migrate Update() from class Error to C++ exceptions

src/command/OtherCommands.cxx

@@ -36,7 +36,6 @@
 #include "ls.hxx"
 #include "mixer/Volume.hxx"
 #include "util/UriUtil.hxx"
-#include "util/Error.hxx"
 #include "util/StringAPI.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "Stats.hxx"
@@ -277,13 +276,10 @@ static CommandResult
 handle_update(Response &r, Database &db,
 	      const char *uri_utf8, bool discard)
 {
-	Error error;
-	unsigned id = db.Update(uri_utf8, discard, error);
+	unsigned id = db.Update(uri_utf8, discard);
 	if (id > 0) {
 		r.Format("updating_db: %i\n", id);
 		return CommandResult::OK;
-	} else if (error.IsDefined()) {
-		return print_error(r, error);
 	} else {
 		/* Database::Update() has returned 0 without setting
 		   the Error: the method is not implemented */

src/db/Interface.hxx

@@ -31,7 +31,6 @@ struct DatabasePlugin;
 struct DatabaseStats;
 struct DatabaseSelection;
 struct LightSong;
-class Error;
 
 class Database {
 	const DatabasePlugin &plugin;
@@ -111,14 +110,15 @@ public:
 	virtual DatabaseStats GetStats(const DatabaseSelection &selection) const = 0;
 
 	/**
-	 * Update the database.  Returns the job id on success, 0 on
-	 * error (with #Error set) and 0 if not implemented (#Error
-	 * not set).
+	 * Update the database.
+	 *
+	 * Throws #std::runtime_error on error.
+	 *
+	 * @return the job id or 0 if not implemented
 	 */
 	virtual unsigned Update(gcc_unused const char *uri_utf8,
-				gcc_unused bool discard,
-				gcc_unused Error &error) {
-		/* not implemented: return 0 and don't set an Error */
+				gcc_unused bool discard) {
+		/* not implemented: return 0 */
 		return 0;
 	}
 

src/db/plugins/ProxyDatabasePlugin.cxx

@@ -124,8 +124,7 @@ public:
 
 	DatabaseStats GetStats(const DatabaseSelection &selection) const override;
 
-	virtual unsigned Update(const char *uri_utf8, bool discard,
-				Error &error) override;
+	unsigned Update(const char *uri_utf8, bool discard) override;
 
 	virtual time_t GetUpdateStamp() const override {
 		return update_stamp;
@@ -820,8 +819,7 @@ ProxyDatabase::GetStats(const DatabaseSelection &selection) const
 }
 
 unsigned
-ProxyDatabase::Update(const char *uri_utf8, bool discard,
-		      gcc_unused Error &error)
+ProxyDatabase::Update(const char *uri_utf8, bool discard)
 {
 	EnsureConnected();