move condition to reduce complexity of Watch

Also add the feature to the README

README.md

@@ -316,10 +316,11 @@ While in watch mode, pressing some keys will perform an action:
 
 * `r` will run tests for the previous event.
 * `d` will run tests for the previous event using `dlv test`, allowing you to 
-  debug a test failure using [delve] A breakpoint will automatically be added at
+  debug a test failure using [delve]. A breakpoint will automatically be added at
   the first line of any tests which failed in the previous run. Additional
   breakpoints can be added with [`runtime.Breakpoint`](https://golang.org/pkg/runtime/#Breakpoint)
   or by using the delve command prompt.
+* `a` will run tests for all packages, by using `./...` as the package selector.
 
 Note that [delve] must be installed in order to use debug (`d`).
 

internal/filewatcher/watch.go

@@ -56,9 +56,6 @@ func Watch(dirs []string, run func(opts RunOptions) error) error {
 			resetTimer(timer)
 
 			redo.ResetTerm()
-			if opts.PkgPath == "" {
-				opts.PkgPath = h.lastPath
-			}
 			if err := h.runTests(opts); err != nil {
 				return fmt.Errorf("failed to rerun tests for %v: %v", opts.PkgPath, err)
 			}
@@ -225,6 +222,9 @@ func (h *handler) handleEvent(event fsnotify.Event) error {
 }
 
 func (h *handler) runTests(opts RunOptions) error {
+	if opts.PkgPath == "" {
+		opts.PkgPath = h.lastPath
+	}
 	fmt.Printf("\nRunning tests in %v\n", opts.PkgPath)
 
 	if err := h.fn(opts); err != nil {