Improve the explanation of `workdir_parent` config (#519)

Fix #512

act_runner adds a '/' before the path (see 5977042b86/internal/app/run/runner.go (L186)) . So `workdir_parent` doesn't need to have the prefix '/'.

If `workdir_parent` has the prefix '/', errors will occur when reading files from the job container.

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/519
Reviewed-by: Jason Song <i@wolfogre.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-committed-by: Zettat123 <zettat123@gmail.com>

internal/app/run/runner.go

@@ -183,7 +183,7 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 	runnerConfig := &runner.Config{
 		// On Linux, Workdir will be like "/<parent_directory>/<owner>/<repo>"
 		// On Windows, Workdir will be like "\<parent_directory>\<owner>\<repo>"
-		Workdir:        filepath.FromSlash(fmt.Sprintf("/%s/%s", r.cfg.Container.WorkdirParent, preset.Repository)),
+		Workdir:        filepath.FromSlash(fmt.Sprintf("/%s/%s", strings.TrimLeft(r.cfg.Container.WorkdirParent, "/"), preset.Repository)),
 		BindWorkdir:    false,
 		ActionCacheDir: filepath.FromSlash(r.cfg.Host.WorkdirParent),
 

internal/pkg/config/config.example.yaml

@@ -63,6 +63,9 @@ container:
   # And other options to be used when the container is started (eg, --add-host=my.gitea.url:host-gateway).
   options:
   # The parent directory of a job's working directory.
+  # NOTE: There is no need to add the first '/' of the path as act_runner will add it automatically. 
+  # If the path starts with '/', the '/' will be trimmed.
+  # For example, if the parent directory is /path/to/my/dir, workdir_parent should be path/to/my/dir
   # If it's empty, /workspace will be used.
   workdir_parent:
   # Volumes (including bind mounts) can be mounted to containers. Glob syntax is supported, see https://github.com/gobwas/glob