What is a good way to move my MacBook life to a temporary computer, and back to primary computer? I use my MacBook Pro extensively, for work and pleasure. I have a lot of apps and settings. I have a ton of data in my Calendar app and Contacts app. I have a sequence of year-based project directories in ~/Documents/Projects/2019/, ~/Documents/Projects/2018/. I keep backups on two different drives.

And this MacBook Pro is broken, so I have to repair it. Repairs will take a week. I don't want to stop all that activity for a week. I want to move enough of my apps and settings and data to a temporary computer that I can keep working, then move back to my main computer when it is repaired. 

What is an effective way to stop changes on my main computer, transfer all of my state to the temporary computer so that I can work without disruption, then transfer all of my state back to the main computer when it returns? 

Note that it's important to have a clean way to be able to keep accumulating project data on the temporary computer, and to move all that project data seamlessly back to the main computer when it returns.

I have a file server, which keeps archives of the past year's project directories. Let's assume that I can copy ~/Documents/Projects/2018/ and earlier to that server, and delete them from my main computer. Thus what I really want to transfer is what is in my home directory outside this year's projects, and apps and settings, and the accumulated project data from the time I am on the temporary computer.

Here are some assumptions to clarify the problem:


I have access to the temporary computer for enough overlap time (a day? a week?) before and after, to perform the transfer
The main computer still functions. It can do its part in the transfer. I can delay the repair until a convenient time.
I have access to plenty of storage locally
I want to avoid cloud storage in favour of local storage which I control
I am willing to buy utility software if it helps
I am comfortable running sysadmin tools, using the command line, etc.
I need a way to delete all my data from the temporary computer when I am done
It would be nice, but not essential, to delete the data on my main computer while it is in for repair


The temporary computer might be a rental, in which case let's assume I could install or delete anything I want, because they will re-image the system when they get it back. Or, the temporary computer might be one of my spare laptops, in which case I can create a new user account for temporary use, and delete it after, but I can't completely blow up the contents of the disk.

I especially hope for answers which describe something you actually do, and which has worked well for you.
Make a complete copy of the primary computer's hard drive using Carbon Copy Cloner to an external SSD / hard drive. Boot the secondary computer from this new disk (turn off computer, connect drive, hold option when restarting to select it as the boot disk). Booted from the external drive, the secondary computer will be just like the primary one now, same files and configuration.

When the primary computer comes back, use CCC again to copy the data from the external drive back to its internal hard drive.