Minor log fixups for snapshots (#4113)

* Fix log message during hierarchy merging so it's not as confusing
* add reason for making a snapshot. This can be used to separate out later messages into item data snapshot and details snapshot during debugging

---

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

#### Test Plan

- [x] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

src/internal/kopia/upload.go

@@ -877,8 +877,8 @@ func traverseBaseDir(
 	stats *count.Bus,
 ) error {
 	ctx = clues.Add(ctx,
-		"old_dir_path", oldDirPath,
-		"expected_dir_path", expectedDirPath)
+		"old_parent_dir_path", oldDirPath,
+		"expected_parent_dir_path", expectedDirPath)
 
 	if depth >= maxInflateTraversalDepth {
 		return clues.New("base snapshot tree too tall").WithClues(ctx)

src/internal/operations/backup.go

@@ -492,7 +492,10 @@ func consumeBackupCollections(
 	isIncremental bool,
 	errs *fault.Bus,
 ) (*kopia.BackupStats, *details.Builder, kopia.DetailsMergeInfoer, error) {
-	ctx = clues.Add(ctx, "collection_source", "operations")
+	ctx = clues.Add(
+		ctx,
+		"collection_source", "operations",
+		"snapshot_type", "item data")
 
 	progressBar := observe.MessageWithCompletion(ctx, "Backing up data")
 	defer close(progressBar)

src/internal/streamstore/streamstore.go

@@ -61,6 +61,8 @@ func (ss *storeStreamer) Collect(ctx context.Context, col Collectable) error {
 
 // Write persists the collected objects in the stream store
 func (ss *storeStreamer) Write(ctx context.Context, errs *fault.Bus) (string, error) {
+	ctx = clues.Add(ctx, "snapshot_type", "stream store")
+
 	id, err := write(ctx, ss.kw, ss.dbcs, errs)
 	if err != nil {
 		return "", clues.Wrap(err, "writing to stream store")