the latter is missing from OpenBSD and maybe other distros.
* improve performance and avoid head-of-line blocking on slow storage
+
+* share "git cat-file --batch" processes across inboxes to avoid
+ bumping into /proc/sys/fs/pipe-user-pages-* limits
+
+* make "git cat-file --batch" detect unlinked packfiles so we don't
+ have to restart processes (very long-term)
+
+* support searching based on `git-patch-id --stable` to improve
+ bidirectional mapping of commits <=> emails