Add 'databases' command.

cmd/litestream/databases.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+	"text/tabwriter"
+)
+
+type DatabasesCommand struct{}
+
+func (c *DatabasesCommand) Run(ctx context.Context, args []string) (err error) {
+	var configPath string
+	fs := flag.NewFlagSet("litestream-databases", flag.ContinueOnError)
+	registerConfigFlag(fs, &configPath)
+	fs.Usage = c.Usage
+	if err := fs.Parse(args); err != nil {
+		return err
+	} else if fs.NArg() != 0 {
+		return fmt.Errorf("too many argument")
+	}
+
+	// Load configuration.
+	if configPath == "" {
+		return errors.New("-config required")
+	}
+	config, err := ReadConfigFile(configPath)
+	if err != nil {
+		return err
+	}
+
+	// List all databases.
+	w := tabwriter.NewWriter(os.Stdout, 0, 8, 1, '\t', 0)
+	fmt.Fprintln(w, "path\treplicas")
+	for _, dbConfig := range config.DBs {
+		db, err := newDBFromConfig(dbConfig)
+		if err != nil {
+			return err
+		}
+
+		var replicaNames []string
+		for _, r := range db.Replicas {
+			replicaNames = append(replicaNames, r.Name())
+		}
+
+		fmt.Fprintf(w, "%s\t%s\n",
+			db.Path(),
+			strings.Join(replicaNames, ","),
+		)
+	}
+	w.Flush()
+
+	return nil
+}
+
+func (c *DatabasesCommand) Usage() {
+	fmt.Printf(`
+The databases command lists all databases in the configuration file.
+
+Usage:
+
+	litestream databases [arguments]
+
+Arguments:
+
+	-config PATH
+	    Specifies the configuration file.
+	    Defaults to %s
+
+`[1:],
+		DefaultConfigPath,
+	)
+}

cmd/litestream/generations.go

@@ -14,10 +14,6 @@ import (
 
 type GenerationsCommand struct{}
 
-func NewGenerationsCommand() *GenerationsCommand {
-	return &GenerationsCommand{}
-}
-
 func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error) {
 	var configPath string
 	fs := flag.NewFlagSet("litestream-generations", flag.ContinueOnError)

cmd/litestream/main.go

@@ -48,6 +48,8 @@ func (m *Main) Run(ctx context.Context, args []string) (err error) {
 	}
 
 	switch cmd {
+	case "databases":
+		return (&DatabasesCommand{}).Run(ctx, args)
 	case "generations":
 		return (&GenerationsCommand{}).Run(ctx, args)
 	case "replicate":

cmd/litestream/replicate.go

@@ -19,10 +19,6 @@ type ReplicateCommand struct {
 	DBs []*litestream.DB
 }
 
-func NewReplicateCommand() *ReplicateCommand {
-	return &ReplicateCommand{}
-}
-
 // Run loads all databases specified in the configuration.
 func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-replicate", flag.ContinueOnError)

cmd/litestream/restore.go

@@ -17,10 +17,6 @@ type RestoreCommand struct {
 	DBPath string
 }
 
-func NewRestoreCommand() *RestoreCommand {
-	return &RestoreCommand{}
-}
-
 func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
 	var configPath string
 	var opt litestream.RestoreOptions

cmd/litestream/snapshots.go

@@ -15,10 +15,6 @@ import (
 
 type SnapshotsCommand struct{}
 
-func NewSnapshotsCommand() *SnapshotsCommand {
-	return &SnapshotsCommand{}
-}
-
 func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
 	var configPath string
 	fs := flag.NewFlagSet("litestream-snapshots", flag.ContinueOnError)

cmd/litestream/wal.go

@@ -15,10 +15,6 @@ import (
 
 type WALCommand struct{}
 
-func NewWALCommand() *WALCommand {
-	return &WALCommand{}
-}
-
 func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
 	var configPath string
 	fs := flag.NewFlagSet("litestream-wal", flag.ContinueOnError)