access: a shallow read shows only the way through where the user reads partly

Review 4, F4: `?shallow=true` kept every entry the user may at least pass through, and
a shallow read inlines short scalars' values with their types and sizes. A scalar at a
level a `*` passes through (a capability on `data/*/public`, an entry `data/count:
42`) showed its value though no capability covers it; before `*`, only a scalar where
a capability expected a map did.

Now an entry the user may read only partly is shown only as the way through it is: a
map, with no more than its type (not its size, the number of its keys); anything else
there (a scalar, a list, which a deep read leaves out too) isn't shown. Entries it may
read whole are as they were.

1 files changed, 3 insertions, 1 deletions

diff --git a/docs/access.md b/docs/access.md
index 1385950..3877dff 100644
--- a/docs/access.md
+++ b/docs/access.md
@@ -70,7 +70,9 @@ change to it counts on a node as soon as it has reached it.
   sees the keys on the way to what it may read, as a directory one may pass through
   but not list (a capability on `servers/eu` shows `servers` with `eu` alone in it),
   and nothing else; a list on the way is left out whole, as its items have no paths of
-  their own. Native forms (`text/plain` of a map, a counter as its own type) only of
+  their own. A shallow read (`?shallow=true`) shows such a map as a map and no more (no
+  size), and nothing beside the way: a scalar at a `*` no capability covers stays
+  hidden. Native forms (`text/plain` of a map, a counter as its own type) only of
   what it may read whole. What a write answers with is what was written. A stream
   shows what the user could read when it opened.
 * **Protocol data** is in the store too, under `_continuum`: `read` and `write` on it