Re: [PATCH] Teach "git add" and friends to be paranoid

> Currently, we calculate SHA-1, then lookup whether the object with this
> SHA-1 exists, and if it does not, then deflate and write it to the
> object storage. So, we avoid deflate and write cost if this object
> already exists. Moreover, when we deflate data, we create the temporary
> file in the same directory where the target object will be stored, thus
> avoiding cross-directory rename (which is important for some reason, but
> I don't remember why).  So, creating the temporary file requires the
> knowledge first two digits of SHA-1, which you cannot know without
> calculation SHA-1.