Implement Cobra CLI tooling, Viper config tooling (#336)

* start pulling out + replacing urfave and config

* replace many many instances of config

* move more stuff => viper

* properly remove urfave

* move some flags to root command

* add testrig commands to root

* alias config file keys

* start adding cli parsing tests

* reorder viper init

* remove config path alias

* fmt

* change config file keys to non-nested

* we're more or less in business now

* tidy up the common func

* go fmt

* get tests passing again

* add note about the cliparsing tests

* reorganize

* update docs with changes

* structure cmd dir better

* rename + move some files around

* fix dangling comma

cmd/gotosocial/common.go

@@ -0,0 +1,64 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+	"github.com/superseriousbusiness/gotosocial/cmd/gotosocial/action"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+// preRun should be run in the pre-run stage of every cobra command.
+// The goal here is to initialize the viper config store, and also read in
+// the config file (if present).
+//
+// The order of these is important: the init-config function reads the location
+// of the config file from the viper store so that it can be picked up by either
+// env vars or cli flag.
+func preRun(cmd *cobra.Command) error {
+	if err := config.InitViper(cmd.Flags()); err != nil {
+		return fmt.Errorf("error initializing viper: %s", err)
+	}
+
+	if err := config.ReadFromFile(); err != nil {
+		return fmt.Errorf("error initializing config: %s", err)
+	}
+
+	return nil
+}
+
+// run should be used during the run stage of every cobra command.
+// The idea here is to take a GTSAction and run it with the given
+// context, after initializing any last-minute things like loggers etc.
+func run(ctx context.Context, action action.GTSAction) error {
+	// if log level has been set...
+	if logLevel := viper.GetString(config.Keys.LogLevel); logLevel != "" {
+		// then try to initialize the logger to that level
+		if err := log.Initialize(logLevel); err != nil {
+			return fmt.Errorf("error initializing log: %s", err)
+		}
+	}
+
+	return action(ctx)
+}