Reads/writes are a little faster with the text format,
and it's far more useful. E.g., it allows external manipulation
and inspection of the analysis.
We don't gzip the output. It does greatly shrink the files,
however it makes reads and writes 1.5x-2x slower, and we're
optimizing for speed over compactness.
We store `Seq[xsbt.api.Compilation]` in `Analysis`. Compilation are
being appended to sequence for every iteration of the incremental
compiler.
Note that `Compilation`s are never removed from the sequence unless
you start from scratch with empty `Analysis`. You can do that by using
sbt's `clean` command.
The main use-case for using `compilations` field is to determine how
many iterations it took to compilen give code. The `Compilation` object
are also stored in `Source` objects so there's an indirect way to recover
information about files being recompiled in every iteration.
Since `Analysis` is persisted you can use this mechanism to track entire
sessions spanning multiple `compile` commands.