In git, is there a simple way of introducing an unrelated branch to a repository?

Question

While helping a friend with a git problem today, I had to introduce a branch that needed to be totally separate from the master branch. The contents of this bra

Answer 1

If your existing content was already committed, you now (Git 2.18 Q2 2018) can extract it into its own new orphan branch, since the implementation of "git rebase -i --root" has been updated to use the sequencer machinery more.

That sequencer is the one now allowing to transplant the whole topology of commit graph elsewhere.

See commit 8fa6eea, commit 9c85a1c, commit ebddf39, commit 21d0764, commit d87d48b, commit ba97aea (03 May 2018) by Johannes Schindelin (dscho).
^{(Merged by Junio C Hamano -- gitster -- in commit c5aa4bc, 30 May 2018)}

sequencer: allow introducing new root commits

In the context of the new --rebase-merges mode, which was designed specifically to allow for changing the existing branch topology liberally, a user may want to extract commits into a completely fresh branch that starts with a newly-created root commit.

This is now possible by inserting the command reset [new root] before picking the commit that wants to become a root commit. Example:

reset [new root]
pick 012345 a commit that is about to become a root commit
pick 234567 this commit will have the previous one as parent

This does not conflict with other uses of the reset command because [new root] is not (part of) a valid ref name: both the opening bracket as well as the space are illegal in ref names.