Fix filer.sync retry on stale chunk (#8298)

* Fix filer.sync stale chunk uploads

* Tweak filersink stale logging

weed/replication/sink/filersink/fetch_write_test.go

@@ -0,0 +1,79 @@
+package filersink
+
+import (
+	"testing"
+
+	"github.com/seaweedfs/seaweedfs/weed/replication/source"
+	"github.com/seaweedfs/seaweedfs/weed/util"
+)
+
+func TestTargetPathToSourcePath(t *testing.T) {
+	tests := []struct {
+		name       string
+		targetRoot string
+		sourceRoot string
+		targetPath string
+		wantPath   util.FullPath
+		wantOK     bool
+	}{
+		{
+			name:       "basic mapping",
+			targetRoot: "/target",
+			sourceRoot: "/source",
+			targetPath: "/target/path/file.txt",
+			wantPath:   "/source/path/file.txt",
+			wantOK:     true,
+		},
+		{
+			name:       "trailing slash roots",
+			targetRoot: "/target/",
+			sourceRoot: "/source/",
+			targetPath: "/target/path/file.txt",
+			wantPath:   "/source/path/file.txt",
+			wantOK:     true,
+		},
+		{
+			name:       "root target mapping",
+			targetRoot: "/",
+			sourceRoot: "/source",
+			targetPath: "/path/file.txt",
+			wantPath:   "/source/path/file.txt",
+			wantOK:     true,
+		},
+		{
+			name:       "target root itself",
+			targetRoot: "/target",
+			sourceRoot: "/source",
+			targetPath: "/target",
+			wantPath:   "/source",
+			wantOK:     true,
+		},
+		{
+			name:       "outside target root",
+			targetRoot: "/target",
+			sourceRoot: "/source",
+			targetPath: "/other/path/file.txt",
+			wantPath:   "",
+			wantOK:     false,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			fs := &FilerSink{
+				dir: tc.targetRoot,
+				filerSource: &source.FilerSource{
+					Dir: tc.sourceRoot,
+				},
+			}
+
+			gotPath, ok := fs.targetPathToSourcePath(tc.targetPath)
+			if ok != tc.wantOK {
+				t.Fatalf("ok mismatch: got %v, want %v", ok, tc.wantOK)
+			}
+			if gotPath != tc.wantPath {
+				t.Fatalf("path mismatch: got %q, want %q", gotPath, tc.wantPath)
+			}
+		})
+	}
+}