Consider changing directory fanout scheme in "Annex A: Filesystem Storage"

[alilleybrinker]

Per @jsgf's comment in #37:

${OMNIBOR_DIR}/objects/${Artifact Identifier Type uri prefix with ':' replaced by '_'}/${OmniBORID:0:2}/${OmniBORID:2:}

The two-digits/rest-of-digits technique for doing directory fanout has always bugged me. Why not do two-digits/all-digits just so that you can do, for example find -name full-id without having to muck about?

This has not yet been resolved. The options so far presented are:

• Keep as-is: Continue to structure directories with the first two characters of the ID as the outer directory name, and the remaining characters in the interior directory.
• Change to Jeremy's scheme: Continue using the first two characters of the ID for the outer directory name, but then use all characters in the interior directory.

Considerations:

• The existing scheme matches what Git does; may be more familiar to some consumers (human and automated) of OmniBOR data.
• Duplicating the initial two characters results in longer names. Some may object to the duplication / waste of the two additional characters. Windows has a limit on path names, so the additional two characters may constrain valid OMNIBOR_DIR settings on Windows.
• Having the full name in the interior path makes finding the relevant data easier (as Jeremy suggests with the find -name <full-id> command).

There may be additional options for what to do here as well.

[alilleybrinker]

The spec has pretty solidly settled on keeping the existing scheme, which matches Git's own behavior, helps keep paths shorter (a potential issue on some filesystems with a small max path length, as can happen on Windows), and this behavior is also what the OmniBOR Rust library and CLI do.