Denis Cucchietti:
The com-liferay-petra repository was the subrepository corresponding
to the modules/apps/petra
folder in the monorepository. The specific modules within that folder
came from the ongoing attempt at modularizing
com.liferay.util.java, as David mentioned, and com.liferay.portal.kernel.
Subrepositories were originally intended to allow for all of the
different .lpkg files that make up a Liferay release to be released on
separate schedules (essentially, each folder in
modules/apps is its own .lpkg). The idea is that
component teams would commit to the subrepositories (each one managed
by one of Liferay's separate teams), and the monorepository would be a
central reference point for a release.
Most subrepositories, including com-liferay-petra, were discontinued
and no longer kept up to date on the master branch (missing a
.gitrepo file) due to some directory reshuffling that
happened prior to the Liferay 7.1 release.
On the master branch, only two are still maintained: the
subrepositories corresponding to modules/apps/analytics
(.gitrepo is in push mode) and modules/apps/apio-architect
(.gitrepo is in pull mode). On the 7.0.x branch, many of
the other subrepositories are still maintained in push mode.
