add builtin 'select' command to change selection

comp.go

@@ -46,6 +46,7 @@ var (
 		"sync",
 		"echo",
 		"cd",
+		"select",
 		"push",
 	}
 

doc.go

@@ -47,6 +47,7 @@ The following commands are provided by lf without default keybindings:
     sync    synchronizes yanked/deleted files with server
     echo    prints its arguments to the message line
     cd      changes working directory to its argument
+    select  changes current file selection to its argument
     push    simulate key pushes given in its argument
 
 The following command line commands are provided by lf with default

docstring.go

@@ -51,6 +51,7 @@ The following commands are provided by lf without default keybindings:
     sync    synchronizes yanked/deleted files with server
     echo    prints its arguments to the message line
     cd      changes working directory to its argument
+    select  changes current file selection to its argument
     push    simulate key pushes given in its argument
 
 The following command line commands are provided by lf with default

eval.go

@@ -387,6 +387,17 @@ func (e *callExpr) eval(app *app, args []string) {
 		}
 		app.ui.loadFile(app.nav)
 		app.ui.loadFileInfo(app.nav)
+	case "select":
+		if len(e.args) != 1 {
+			app.ui.print("select: requires an argument")
+			return
+		}
+		if err := app.nav.find(e.args[0]); err != nil {
+			app.ui.printf("%s", err)
+			return
+		}
+		app.ui.loadFile(app.nav)
+		app.ui.loadFileInfo(app.nav)
 	case "push":
 		if len(e.args) > 0 {
 			log.Println("pushing keys", e.args[0])

nav.go

@@ -260,6 +260,7 @@ func (nav *nav) getDirs(wd string) {
 
 	for curr, base := wd, ""; !isRoot(base); curr, base = filepath.Dir(curr), filepath.Base(curr) {
 		dir := nav.loadDir(curr)
+		dir.find(base, nav.height)
 		dirs = append(dirs, dir)
 	}
 
@@ -618,6 +619,30 @@ func (nav *nav) cd(wd string) error {
 	return nil
 }
 
+func (nav *nav) find(path string) error {
+	lstat, err := os.Stat(path)
+	if err != nil {
+		return fmt.Errorf("select: %s", err)
+	}
+
+	dir := filepath.Dir(path)
+
+	if err := nav.cd(dir); err != nil {
+		return fmt.Errorf("select: %s", err)
+	}
+
+	base := filepath.Base(path)
+
+	last := nav.dirs[len(nav.dirs)-1]
+	if last.loading {
+		last.fi = append(last.fi, &file{FileInfo: lstat})
+	} else {
+		last.find(base, nav.height)
+	}
+
+	return nil
+}
+
 func match(pattern, name string) (matched bool, err error) {
 	if gOpts.ignorecase {
 		lpattern := strings.ToLower(pattern)