Git: how to remove history before a specific commit

Question

I.e., I have:

root -- c1 -- c2 -- .. - c1000 -- c1001 -- c1002 -- .. -- c2000 -- top

and I want to have:

root = c1000 -- c1         


        

Answer 1

Easiest way is with a git graft. If you edit the file .git/info/grafts, you can put lines in the file of the format

[ref] [parent1] [parent2] ...

Any commits referenced on the left side are then treated as if the parents listed on the right are the parents of that commit. So you can insert a line like

c1000

and it will be treated as though it has no parents. This can then be "baked in stone" by running git-filter-branch.