anch.  Some of these are for supporting the convenience
functions provided by git-filter-branch (such as map()), while others
are for keeping track of internal state (but could have also been
accessed by user filters; one of git-filter-branch&#8217;s regression tests
does so).  This essentially amounts to using the filesystem as an IPC
mechanism between git-filter-branch and the user-provided filters.
Disks tend to be a slow IPC mechanism, and writing these files also
effectively represents a forced synchro