Since writing multiple objects may all already exist in a single packfile, avoid freshening that packfile repeatedly in a tight loop. Instead, only freshen pack files every 2 seconds.
When writing an object, we calculate its OID and see if it exists in the object database. If it does, we need to freshen the file that contains it.
git_index_entry__init_from_stat: set nsec fields in entry stats
Instead of relying on the size and timestamp, which can hide changes performed in the same second, hash the file content's when we care about detecting changes.
Untangle git_futils_mkdir from git_futils_mkdir_ext - the latter assumes that we own everything beneath the base, as if it were being called with a base of the repository or working directory, and is tailored towards checkout and ensuring that there is no bogosity beneath the base that must be cleaned up. This is (at best) slow and (at worst) unsafe in the larger context of a filesystem where we do not own things and cannot do things like unlink symlinks that are in our way.
On case insensitive filesystems, we may have files in the working directory that case fold to a name we want to write. Remove those files (by default) so that we will not end up with a filename that has the unexpected case.
Checkout can now provide performance data about the number of (some) syscalls performed using an optional callback.
When passed the LINK_FILES flag, the recursive copy will hardlink files instead of copying them.