This adds support for tombstoned files to clay. It does not include any
way to actually tombstone them; that is left for later.
This allows tombstoning at the level of a file. Precisely, this expands
+blob:clay by adding a %dead case:
+$ blob :: fs blob
$% [%delta p=lobe q=[p=mark q=lobe] r=page] :: delta on q
[%direct p=lobe q=page] :: immediate
[%dead p=lobe ~] :: tombstone
== ::
Thus, we maintain the invariant that every lobe corresponds to a blob,
but now a blob may be an explicit tombstone.
Details:
- This has not been tested at all, except that it compiles and boots.
- This does not have a state adapter from master. The only state change
is the definition of +cach.
- Additionally, out-of-date ships may unexpectedly receive a %dead blob
from a foreign clay which would interfere with their ability to download
that desk. No code changes necessary, but sponsors should avoid
tombstoning files in %base for a while so their children can get the
update.
- A merge will only fail if the tombstoned file conflicts with another
change. Note that as written, merging from a past desk *can* bring a
tombstoned file to the head of a desk. Possibly this shouldn't be
allowed.
This also includes a couple refactors that were made possible by ford
fusion (since everything is synchronous now) but never got done. In
both cases we get to remove a monad, which simplifies the code
considerably.
- refactor +merge's error handling to use !!/mule instead of threading
through errors
- refactor all +read-* functions and related parts of +try-fill-sub to
eagerly convert lobes to cages.
We also add support reading %a/b/c/e/f/r/x from past and foreign desks,
when possible. Apologies that all of these are in one commit, it was
all a single chunk of work.
This is a draft until we have a way to tombstone. I suspect we'll want
to have a mechanism of keeping track of gc roots and trace to remove,
but this PR doesn't suggest any particular strategy.
Previously, if trying to bind to an endpoint that was already bound to,
eyre would reject it. This doesn't play very nicely in a softdist world
where uninstalled apps might not get a chance to clean up, and apps
might re-bind simply for being re-installed.
Here we change eyre to overwrite an existing binding if it conflicts
with the new one to be added.
