Merge pull request jpillora#57 from tgulacsi/windows56

Implement weird overwrite logic for windows

proc_master.go

@@ -292,7 +292,7 @@ func (mp *master) fetch() {
 		return
 	}
 	//overwrite!
-	if err := move(mp.binPath, tmpBinPath); err != nil {
+	if err := overwrite(mp.binPath, tmpBinPath); err != nil {
 		mp.warnf("failed to overwrite binary: %s", err)
 		return
 	}

proc_slave_others.go

@@ -28,3 +28,7 @@ func (sp *slave) watchParent() error {
 	}()
 	return nil
 }
+
+func overwrite(dst, src string) error {
+	return move(dst, src)
+}

proc_slave_windows.go

@@ -5,9 +5,11 @@ package overseer
 import (
 	"context"
 	"fmt"
-	"github.com/StackExchange/wmi"
 	"os"
+	"strings"
 	"time"
+
+	"github.com/StackExchange/wmi"
 )
 
 var (
@@ -112,3 +114,16 @@ func WMIQueryWithContext(ctx context.Context, query string, dst interface{}, con
 		return err
 	}
 }
+
+// overwrite: see https://github.com/jpillora/overseer/issues/56#issuecomment-656405955
+func overwrite(dst, src string) error {
+	old := strings.TrimSuffix(dst, ".exe") + "-old.exe"
+	if err := move(old, dst); err != nil {
+		return err
+	}
+	if err := move(dst, src); err != nil {
+		return err
+	}
+	os.Remove(old)
+	return nil
+}