Add sfdupes info: show the database's details (closes #117)

info prints the database's path and source, the sizes of the database
file and its -wal file, when the database file last changed, the schema
version and the record counts, one per line as a name, a tab and the
value. It opens the database as report does and shows an open and a
count phase on stderr. The schema version and the counts come from one
read-only transaction, the counts from one query.

seedDatabase now closes test databases out of WAL mode, as scan does;
otherwise info's own connection creates an empty -wal file. The open
phase's name and text became constants for the linter, and the scan
command moved to newScanCommand to keep newRootCommand short enough.

Judgement call: the lines are written after the last display ends, so they skip the display's stdout writer.

Model: opus-5-5

report_test.go

@@ -29,7 +29,8 @@ func awkwardPairRecs() []scanRec {
 	}
 }
 
-// seedDatabase writes recs into a fresh database and returns its path.
+// seedDatabase writes recs into a fresh database, closes it as scan
+// does, out of WAL mode, and returns its path.
 func seedDatabase(t *testing.T, recs []scanRec) string {
 	t.Helper()
 
@@ -45,10 +46,7 @@ func seedDatabase(t *testing.T, recs []scanRec) string {
 		t.Fatal(err)
 	}
 
-	err = db.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
+	closeScanDatabase(t.Context(), db, path)
 
 	return path
 }