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.

So the equivalent of "git gc --aggressive" - but done properly - is to
do (overnight) something like

git repack -a -d --depth=250 --window=250

where that depth thing is just about how deep the delta chains can be
(make them longer for old history - it's worth the space overhead), and
the window thing is about how big an object window we want each delta
candidate to scan.

And here, you might well want to add the "-f" flag (which is the "drop all
old deltas", since you now are actually trying to make sure that this one
actually finds good candidates.