perf: speed up action downloads (#1209)

An action pinned to a full commit hash cloned the whole repository, and a cached one hit the network on every run. Now only the pinned commit is fetched at depth 1, a cached commit is reused with no network at all, and the action's `.git` directory no longer ships into the job container, matching GitHub.

```
repo                  cold ms         warm ms       cache KiB
actions/checkout      5807 → 787    1064 → 12    11492 → 2349
actions/setup-node   15257 → 1013   1365 → 21    64303 → 9924
actions/cache        18782 → 760    1589 → 16    60890 → 12507
actions/setup-go      5513 → 764     589 → 20    16600 → 9104
docker/login-action  25809 → 1225   1288 → 10    81709 → 12503
```

Reviewed-on: https://gitea.com/gitea/runner/pulls/1209
Reviewed-by: bircni <[email protected]>
Co-authored-by: silverwind <[email protected]>

act/container/host_environment.go

@@ -92,7 +92,7 @@ func (e *HostEnvironment) Copy(destPath string, files ...*FileEntry) common.Exec
 	}
 }
 
-func (e *HostEnvironment) CopyDir(destPath, srcPath string, useGitIgnore bool) common.Executor {
+func (e *HostEnvironment) CopyDir(destPath, srcPath string, useGitIgnore, skipGitDir bool) common.Executor {
 	return func(ctx context.Context) error {
 		logger := common.Logger(ctx)
 		srcPrefix := filepath.Dir(srcPath)
@@ -110,9 +110,10 @@ func (e *HostEnvironment) CopyDir(destPath, srcPath string, useGitIgnore bool) c
 			ignorer = gitignore.NewMatcher(ps)
 		}
 		fc := &filecollector.FileCollector{
-			Ignorer:   ignorer,
-			SrcPath:   srcPath,
-			SrcPrefix: srcPrefix,
+			Ignorer:    ignorer,
+			SrcPath:    srcPath,
+			SrcPrefix:  srcPrefix,
+			SkipGitDir: skipGitDir,
 			Handler: &filecollector.CopyCollector{
 				DstDir: destPath,
 			},