feat: shallow clone action repositories (#1053)

## Summary

When a workflow references a remote action (e.g. `uses: actions/checkout@v4`) the runner clones that repository during job setup.
Previously this was always a full clone(every branch and the complete history) even though only a single ref is needed.

This PR makes the runner shallow-clone the requested ref by default (`--depth=1`, single branch), falling back to a full clone when a shallow clone fails.

Notes:
- Existing on-disk caches are reused as-is; there is no forced re-clone on upgrade.

## Changes

- A new `runner.action_shallow_clone` option (default `true`) lets operators opt back into full clones.
- `cloneAtDepth`: attempt a shallow clone; fall back to a full clone when shallow clone fails.
- Keep a shallow cache cheap on update: fetch the single requested ref at depth 1 and skip `pull`.

---------

Co-authored-by: bircni <bircni@icloud.com>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1053
Reviewed-by: Nicolas <bircni@icloud.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-committed-by: Zettat123 <zettat123@gmail.com>

act/runner/reusable_workflow.go

@@ -141,6 +141,7 @@ func cloneRemoteReusableWorkflow(rc *RunContext, cloneURL, ref, targetDirectory,
 			Dir:         targetDirectory,
 			Token:       token,
 			OfflineMode: rc.Config.ActionOfflineMode,
+			Depth:       rc.Config.ActionCloneDepth,
 		})(ctx)
 	}
 }

act/runner/runner.go

@@ -33,6 +33,7 @@ type Config struct {
 	Workdir                            string                                        // path to working directory
 	ActionCacheDir                     string                                        // path used for caching action contents
 	ActionOfflineMode                  bool                                          // when offline, use cached action contents
+	ActionCloneDepth                   int                                           // limit history when cloning an action repo; 0 clones every branch in full
 	BindWorkdir                        bool                                          // bind the workdir to the job container
 	EventName                          string                                        // name of event to run
 	EventPath                          string                                        // path to JSON file to use for event.json in containers

act/runner/step_action_remote.go

@@ -121,6 +121,7 @@ func (sar *stepActionRemote) prepareActionExecutor() common.Executor {
 			Dir:         actionDir,
 			Token:       token,
 			OfflineMode: sar.RunContext.Config.ActionOfflineMode,
+			Depth:       sar.RunContext.Config.ActionCloneDepth,
 
 			InsecureSkipTLS: sar.cloneSkipTLS(), // For Gitea
 		})