Report unknown blob figures for a snapshot whose manifest cannot be read (closes #272)

When remote info could not read a snapshot's manifest, the orphan
figures were unknown but the snapshot's row still gave 0 blobs and 0 B,
in the table and in --json. The row's blob count and blob size are now
unknown, and null in --json.

A directory with no manifest, as an interrupted backup leaves, still
shows 0: the orphan figures count its blobs as orphaned, so it
references none.

Model: opus-5-5

internal/vaultik/info.go

@@ -524,12 +524,12 @@ func (v *Vaultik) printRemoteInfoTable(result *RemoteInfoResult) {
 		v.stdoutf("%s", separator)
 
 		for _, info := range result.Snapshots {
-			blobCount := unknownText
+			blobCount := countUnknown
 			if info.BlobCount != nil {
 				blobCount = humanize.Comma(int64(*info.BlobCount))
 			}
 
-			blobsSize := unknownText
+			blobsSize := countUnknown
 			if info.BlobsSize != nil {
 				blobsSize = ubytes(*info.BlobsSize)
 			}

internal/vaultik/prune_count_test.go

@@ -42,7 +42,7 @@ func TestTableCountForReportSurfacesReadFailure(t *testing.T) {
 	assert.Nil(t, missing, "a failed read is unknown, not a count")
 
 	// The rendered count for a failed read must say unknown, never 0.
-	assert.Equal(t, unknownText, countText(missing))
+	assert.Equal(t, countUnknown, countText(missing))
 	assert.NotEqual(t, "0", countText(missing))
 }
 
@@ -57,7 +57,7 @@ func TestCountTextDistinguishesEmptyFromUnknown(t *testing.T) {
 
 	assert.Equal(t, "0", countText(&zero))
 	assert.Equal(t, "7", countText(&seven))
-	assert.Equal(t, unknownText, countText(nil))
+	assert.Equal(t, countUnknown, countText(nil))
 }
 
 // TestCountDiffUnknownWhenEitherSideUnknown checks that a delta computed

internal/vaultik/snapshot.go

@@ -1756,9 +1756,9 @@ func (v *Vaultik) PruneDatabase() (*PruneResult, error) {
 	return result, nil
 }
 
-// unknownText is what a count or size reads as when it could not be
+// countUnknown is what a count reads as when its query could not be run,
-// determined, distinct from "0", which is a real zero.
+// distinct from "0", which means the table really was empty.
-const unknownText = "unknown"
+const countUnknown = "unknown"
 
 // tableCountForReport returns the row count of a table for the prune
 // summary, or nil if the count could not be read. A read failure is
@@ -1795,7 +1795,7 @@ func countDiff(before, after *int64) *int64 {
 // one that could not be queried.
 func countText(count *int64) string {
 	if count == nil {
-		return unknownText
+		return countUnknown
 	}
 
 	return strconv.FormatInt(*count, 10)