Git creates huge temporary garbage objects

Question

I'd like to use git locally to track changes to a few local files, dispatched over my home directory.

I initialised a repository at ~, then added the few files with git add, and made a few commits. So far so good, .git is 300K large.

Problem is overnight, .git grew to 5.4G, filling my disk (maybe it could grow more). This happened twice : the first time, I re-created the repos, and the second time, git prune fixed it. Before pruning, git count-objects -v reported error: garbage found: .git/objects/95/tmp_obj_....

Edit : One hour after posting, it had happened again (and I pruned again).

Why does it happen, and how to fix it ?

(I tried to group all these files in a single directory with links but could come up with a working solution that would keep the files at their desired locations, but if the problem really comes with the repos being at ~/, then I would seek solutions in this direction.)

git version 1.7.10.4 on Debian GNU/Linux wheezy/sid

Answer 1

Turns out I had another git repository auto-commiting with cron, the script of which had a broken cd in it (so it stayed in ~/, and run git add . >/dev/null, and commit, from there).

_{Many thanks to Alex Shepard for his help in chat, which led to this being pinned down.}