chore(cmd): clean up commands (#9705)

Move infrastructure related commands to under `cmd/infra` and
development stuff to `cmd/dev`. The default build command builds the
regular user facing binaries: syncthing, stdiscosrv, and strelaysrv.

cmd/dev/stwatchfile/main.go

@@ -0,0 +1,98 @@
+// Copyright (C) 2015 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package main
+
+import (
+	"crypto/sha256"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	_ "github.com/syncthing/syncthing/lib/automaxprocs"
+)
+
+func main() {
+	period := flag.Duration("period", 200*time.Millisecond, "Sleep period between checks")
+	flag.Parse()
+
+	file := flag.Arg(0)
+
+	if file == "" {
+		fmt.Println("Expects a path as an argument")
+		return
+	}
+
+	exists := true
+	size := int64(0)
+	mtime := time.Time{}
+	var hash [sha256.Size]byte
+
+	for {
+		time.Sleep(*period)
+
+		newExists := true
+		fi, err := os.Stat(file)
+		if err != nil && os.IsNotExist(err) {
+			newExists = false
+		} else if err != nil {
+			fmt.Println("stat:", err)
+			return
+		}
+
+		if newExists != exists {
+			exists = newExists
+			if !newExists {
+				fmt.Println(file, "does not exist")
+			} else {
+				fmt.Println(file, "appeared")
+			}
+		}
+
+		if !exists {
+			size = 0
+			mtime = time.Time{}
+			hash = [sha256.Size]byte{}
+			continue
+		}
+
+		if fi.IsDir() {
+			fmt.Println(file, "is directory")
+			return
+		}
+		newSize := fi.Size()
+		newMtime := fi.ModTime()
+
+		newHash, err := sha256file(file)
+		if err != nil {
+			fmt.Println("sha256file:", err)
+		}
+
+		if newSize != size || newMtime != mtime || newHash != hash {
+			fmt.Println(file, "Size:", newSize, "Mtime:", newMtime, "Hash:", fmt.Sprintf("%x", newHash))
+			hash = newHash
+			size = newSize
+			mtime = newMtime
+		}
+	}
+}
+
+func sha256file(fname string) (hash [sha256.Size]byte, err error) {
+	f, err := os.Open(fname)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	h := sha256.New()
+	io.Copy(h, f)
+	hb := h.Sum(nil)
+	copy(hash[:], hb)
+
+	return
+}