OurBigBook stores some metadata and outputs it generates/needs inside the
./_out/ directory that it creates inside the --outdir <outdir>.Overview of files it contains:
db.sqlite3: cross file internal link internalspublish: a git clone of the source of the main repository to ensure that untracked files won't accidentally go into the outputpublish/_out/db.sqlite3: like_out/db.sqlite3but from the clean clone of_out/publishpublish/_out/publish: the final generated output directory that gets published, e.g. as in publish to GitHub Pages