Pour choisir le commit le plus ancien à garder...
git log --pretty="%h - %s" --before=2.weeks -1

!/bin/bash

git checkout --orphan temp $1
git commit -m "Truncated history"
git rebase --onto temp $1 master
git branch -D temp

The following 2 commands are optional - they keep your git repo in good shape.

git prune --progress # delete all the objects w/o references
git gc --aggressive # aggressively collect garbage; may take a lot of time on large repos

Invocation: cd to your repository, then git-truncate refspec, where refspec is either a commit’s SHA1 hash-id, or a tag.