Writing the file to the filesystem for all tags is unnecessary if the
content can just be parsed in memory. This improves the performance:
Here the output of `time ./stats.sh`:
old
./stats.sh 5.96s user 26.53s system 94% cpu 34.533 total
new
./stats.sh 5.85s user 22.86s system 102% cpu 28.040 total
So a reduction of 6.5s (23%) is achieved even on a computer with a
decent SSD.
