This was originally introduced by me in #1814 to address #1811. Eyre was not
canceling heartbeat timers on all relevant events making it easy to end
up with an infinite behn loop. This check allowed ships that entered an infinite
loop to recover, as per my comment at
https://github.com/urbit/urbit/pull/1814#discussion_r333477482. Otherwise it's
not necessary.
If both sides changed a file in the same way, %mate used the version in
the mergebase, which is incorrect. This changes it to use the version
in the destination desk.
An example of this issue:
> +cat %/test/hoon
/~zod/home/~2020.9.3..21.41.24..61ed/test/hoon
first
> |merge %scratch our %home
>=
merged with strategy %fine
+ /~zod/scratch/2/test/hoon
> +cat /=scratch=/test
/~zod/scratch/~2020.9.3..21.41.32..408c/test/hoon
first
> *%/test/hoon 'second'
: /~zod/home/3/test/hoon
> *%%%/scratch=/test/hoon 'second'
: /~zod/scratch/3/test/hoon
> |merge %scratch our %home
>=
%fine merge failed, trying %meet
%meet merge failed, trying %mate
merged with strategy %mate
: /~zod/scratch/4/test/hoon
> +cat /=scratch=/test
/~zod/scratch/~2020.9.3..21.42.25..9e8b/test/hoon
first
Ordinarily, eyre cleans up the relevant gall subscriptions whenever a
channel disappears. In yet unresolved erroneous behavior though, it may
leave a gall subscription open, despite wiping the channel from state.
Attempting to pass the response onto the deleted channel anyway results
in an %eyre-no-channel error later in the event. The volume of these
errors can degrade the user experience, as per #3196.
To resolve the annoyance (but not the underlying issue) we detect the
"subscription has no channel" case, and issue a %leave. Doing so
requires additional information in the wire, so we add that in,
refactoring the relevant wire building along the way.
Note that due to the wire requirements, this cannot resolve existing
cases. For that, we depend on bc929ba6d.
As part of the solution to #3196, we need to clean up any gall
subscriptions that eyre didn't properly clean up.
Since detecting that is hard, we opt to just wipe _all_ eyre-originating
subscriptions from gall. We inspect the duct, which isn't good, but it's
only just this once.
The main thing here is that we aggressively check whether we're in
ancestry of another mergebase candidate. This means we don't have to do
a 2nd pass to eliminate redundant candidates.
Change the definition of base-hash to be the mergebase of %home with the
OTA source. This means it's the most recent successfully-applied
update, which is usually the most important information.
Add sour-hash, which is the hash of the most recently *downloaded*
update, regardless of whether it applied successfuly (ie the old
base-hash).
Add a summary of the various hashes at the top of gen/trouble.
Only no-op if the incoming commit's parent is the old head of the desk.
Also move the printing near the end so we can know exactly if anything
changed.
