When setting up a new machine...

[mattjmorrison]

https://stackoverflow.com/a/11357708

download the zip/tarball propose by GitHub
git clone --bare the GitHub repo (so no checkout: it may be easier with your shaky connection)
move the xxx.git directory (renaming it '.git') created by the clone into the uncompressed repo content from step 1.
remove the bare attribute in the .git moved directory: git config --bool core.bare false

If a clone --bare doesn't work, then this approach would not be useful.
And a restartable clone (which was considered in 2009, even formalized as a SoC) isn't yet a reality.