Pretty print in MongoDB shell as default
(note: this is answer to original version of the question, which did not have requirements for "default")
You can ask it to be pretty.
db.collection.find().pretty()
You can add
DBQuery.prototype._prettyShell = true
to your file in $HOME/.mongorc.js
to enable pretty print globally by default.
(note: this is answer to the updated question)
You can just do this on the CLI:
echo DBQuery.prototype._prettyShell = true >> ~/.mongorc.js
And it's always going to output pretty results.