Currently only implemented for local git remotes. May try to add support
to git-annex-shell for ssh remotes later. Could concevably also be
supported by some special remote, although that seems unlikely.
Cronner user this when available, and when not falls back to
fsck --fast --from remote
git annex fsck --from does not itself use this interface.
To do so, I would need to pass --fast and all other options that influence
fsck on to the git annex fsck that it runs inside the remote. And that
seems like a lot of work for a result that would be no better than
cd remote; git annex fsck
This may need to be revisited if git-annex-shell gets support, since it
may be the case that the user cannot ssh to the server to run git-annex
fsck there, but can run git-annex-shell there.
This commit was sponsored by Damien Diederen.
I probably need to improve handling of the PleaseTerminate exception to
kill the fsck process. Also, if fsck finds bad files, something needs
to requeue downloads of them. Otherwise, this should work, but is probably
quite buggy since I have only tested the pure code over the past 2 days.
Extends the index.lock handling to other git lock files. I surveyed
all lock files used by git, and found more than I expected. All are
handled the same in git; it leaves them open while doing the operation,
possibly writing the new file content to the lock file, and then closes
them when done.
The gc.pid file is excluded because it won't affect the normal operation
of the assistant, and waiting for a gc to finish on startup wouldn't be
good.
All threads except the webapp thread wait on the new startup sanity checker
thread to complete, so they won't try to do things with git that fail
due to stale lock files. The webapp thread mostly avoids doing that kind of
thing itself. A few configurators might fail on lock files, but only if the
user is explicitly trying to run them. The webapp needs to start
immediately when the user has opened it, even if there are stale lock
files.
Arranging for the threads to wait on the startup sanity checker was a bit
of a bear. Have to get all the NotificationHandles set up before the
startup sanity checker runs, or they won't see its signal. Perhaps
the NotificationBroadcaster is not the best interface to have used for
this. Oh well, it works.
This commit was sponsored by Michael Jakl
This is motivated by a user report that the assistant was repeatedly
retrying transfers of files that had been deleted (in direct mode, so
removing the only copy).
Note that the glacier code retries failed transfers after a while to retry
downloads that have aged long enough to be available. This is ok; if we're
doing a full transfer scan we'll retry on every file that is still in the
git tree.
Also note that this makes the assistant less likely to get every file
referenced by old revs of the git tree. Not something the assistant tries
to ensure anyway, so I feel this is acceptable.
To support this, a core.gcrypt-id is stored by git-annex inside the git
config of a local gcrypt repository, when setting it up.
That is compared with the remote's cached gcrypt-id. When different, a
drive has been changed. git-annex then looks up the remote config for
the uuid mapped from the core.gcrypt-id, and tweaks the configuration
appropriately. When there is no known config for the uuid, it will refuse to
use the remote.
Requires git 1.8.4 or newer. When it's installed, a background
git check-ignore process is run, and used to efficiently check ignores
whenever a new file is added.
Thanks to Adam Spiers, for getting the necessary support into git for this.
A complication is what to do about files that are gitignored but have
been checked into git anyway. git commands assume the ignore has been
overridden in this case, and not need any more overriding to commit a
changed version.
However, for the assistant to do the same, it would have to run git ls-files
to check if the ignored file is in git. This is somewhat expensive. Or it
could use the running git-cat-file process to query the file that way,
but that requires transferring the whole file content over a pipe, so it
can be quite expensive too, for files that are not git-annex
symlinks.
Now imagine if the user knows that a file or directory tree will be getting
frequent changes, and doesn't want the assistant to sync it, so gitignores
it. The assistant could overload the system with repeated ls-files checks!
So, I've decided that the assistant will not automatically commit changes
to files that are gitignored. This is a tradeoff. Hopefully it won't be a
problem to adjust .gitignore settings to not ignore files you want the
assistant to autocommit, or to manually git annex add files that are listed
in .gitignore.
(This could be revisited if git-annex gets access to an interface to check
the content of the index w/o forking a git command. This could be libgit2,
or perhaps a separate git cat-file --batch-check process, so it wouldn't
need to ship over the whole file content.)
This commit was sponsored by Francois Marier. Thanks!
This bug was introduced in 82a6db8fe8,
which improved handling of adding very large numbers of files by ensuring
that a minimum number of max size commits (5000 files each) were done.
I accidentially made it wait for another change to appear after such a max
size commit, even if a lot of queued changes were already accumulated.
That resulted in a stall when it got to the end. Now fixed to not wait
any longer than necessary to ensure the watcher has had time to wake back
up after the max size commit.
This commit was sponsored by Michael Linksvayer. Thanks!
This is a laziness problem. Despite the bang pattern on newfiles, the list
was not being fully evaluated before cleanup was called. Moving cleanup out
to after the list is actually used fixes this.
More evidence that I should be using ResourceT or pipes, if any was needed.
This affected both the hourly NetWatcherFallback thread and the syncing
when network connection is detected.
It was a reversion of sorts, introduced in
8861e270be, when annex-ignore was changed to
not control git syncing. I forgot to make it check annex-sync at that
point.
This is a compromise. I would like to nice every thread except for the
webapp thread, but it's not practical to do so. That would need every
thread to run as a bound thread, which could add significant overhead.
And any forkIO would escape the nice level.
I noticed that when my modem hung up and redialed, my xmpp client was left
sending messages into the void. This will also handle any idle
disconnection issues.
I hope this will be easier to reason about, and less buggy. It was
certianly easier to write!
An immediate benefit is that with a traversable queue of push requests to
select from, the threads can be a lot fairer about choosing which client to
service next.
This will avoid losing any messages received from 1 client when a push
involving another client is running.
Additionally, the handling of push initiation is improved,
it's no longer allowed to run multiples of the same type of push to
the same client.
Still stalls sometimes :(
Observed: With 2 xmpp clients, one would sometimes stop responding
to CanPush messages. Often it was in the middle of a receive-pack
of its own (or was waiting for a failed one to time out).
Now these are always immediately responded to, which is fine; the point
of CanPush is to find out if there's another client out there that's
interested in our push.
Also, in queueNetPushMessage, queue push initiation messages when
we're already running the side of the push they would initiate.
Before, these messages were sent into the netMessagesPush channel,
which was wrong. The xmpp send-pack and receive-pack code discarded
such messages.
This still doesn't make XMPP push 100% robust. In testing, I am seeing
it sometimes try to run two send-packs, or two receive-packs at once
to the same client (probably because the client sent two requests).
Also, I'm seeing rather a lot of cases where it stalls out until it
runs into the 120 second timeout and cancels a push.
And finally, there seems to be a bug in runPush. I have logs that
show it running its setup action, but never its cleanup action.
How is this possible given its use of E.bracket? Either some exception
is finding its way through, or the action somehow stalls forever.
When this happens, one of the 2 clients stops syncing.
This fixes a bug with git annex add in direct mode. If some files already
existed in the tree pointing at the same key as a file that was just added,
and their content was not present, add neglected to copy the content to
those files.
I also changed the behavior of moveAnnex slightly: When content is moved
into the annex in direct mode, it does not overwrite any content already
present in direct mode files. That content may be modified after all.
Unless the request is for repo uuid we already know. This way, if A1 pairs
with friend B1, and B1 pairs with device B2, then B1 can request A1 pair
with it and no confirmation is needed. (In future, may want to try to do
that automatically, to make a more robust network.)
Observed that the pushed refs were received, but not merged into master.
The merger never saw an add event for these refs. Either git is not writing
to a new file and renaming it into place, or the inotify code didn't notice
that. Changed it to also watch for modify events and that seems to have
fixed it!
Without this, a very large batch add has commits of sizes approx
5000, 2500, 1250, etc down to 10, and then starts over at 5000.
This fixes it so it's 5000+ every time.
That hook updates associated file bookkeeping info for direct mode.
But, everything already called addAssociatedFile when adding/changing a
file. It only needed to also call removeAssociatedFile when deleting a file,
or a directory.
This should make bulk adds faster, by some possibly significant amount.
Bulk removals may be a little slower, since it has to use catKeyFile now
on each removed file, but will still be faster than adds.
There's a tradeoff between making less frequent commits, and
needing to use memory to store all the changes that are coming
in. At 10 thousand, it needs 150 mb of memory. 5 thousand drops
that down to 90 mb or so.
This also turns out to have significant imact on total run time.
I benchmarked 10k changes taking 27 minutes. But two 5k batches
took only 21 minutes.
If an add failed, we should lose the KeySource, since it, presumably,
differs due to a change that was made to the file.
(The locked down file is already deleted.)
Turns out that a lot of the time spent in a bulk add was just updating the
add alert to rotate through each file that was added. Showing one alert
makes for a significant speedup.
Also, when the webapp is open, this makes it take quite a lot less cpu
during bulk adds.
Also, it lets the user know when a bulk add happened, which is sorta
nice..
This is so git remotes on servers without git-annex installed can be used
to keep clients' git repos in sync.
This is a behavior change, but since annex-sync can be set to disable
syncing with a remote, I think it's acceptable.
Incidentially should work around the last problem that prevented the webapp
building on Android. (Except for a few places I need to clean up after
hand-fixing the spliced TH code.)
* addurl: Register transfer so the webapp can see it.
* addurl: Automatically retry downloads that fail, as long as some
additional content was downloaded.
Fixed by storing a list of cached inodes for a key, instead of just one.
Backwards compatability note: An old git-annex version will fail to parse
an inode cache file that has been written by a new version, and has
multiple items. It will succees if just one. So old git-annexes will have
even worse behavior when there are duplicated files, if that is possible.
I don't think it will be a problem. (Famous last words.)
Also, note that it doesn't expire old and unused inode caches for a key.
It would be possible to add this if needed; just look through the
associated files for a key and if there are more cached inodes, throw out
any not corresponding to associated files. Unless a file is being copied
repeatedly and the old copy deleted, this lack of expiry should not be a
problem.
* since this is a crippled filesystem anyway, git-annex doesn't use
symlinks on it
* so there's no reason to use the mixed case hash directories that we're
stuck using to avoid breaking everyone's symlinks to the content
* so we can do what is already done for all bare repos, and make non-bare
repos on crippled filesystems use the all-lower case hash directories
* which are, happily, all 3 letters long, so they cannot conflict with
mixed case hash directories
* so I was able to 100% fix this and even resuming `git annex add` in the
test case will recover and it will all just work.
This avoids commit churn by the assistant when eg,
replacing a file with a symlink.
But, just as importantly, it prevents the working tree being left with a
deleted file if git-annex, or perhaps the whole system, crashes at the
wrong time.
(It also probably avoids confusing displays in file managers.)
My test case for this bug is to have the assistant running and syncing to
a remote, and create a file in the annex. Then at the command line run
git annex drop. The assistant sees that the file is gone, sees it's a wanted
file, and downloads it from the remote.
With a directory special remote and a small file, I was seeing around 1
time in 3, a race where the file got unstaged from git after it got
downloaded.
Looking at what direct mode content managing code does in this case, it
deletes the symlink, and then adds the file content back. It would be
possible, sometimes, to avoid removing the symlink and do this atomically.
And I probably should.. but in some cases, particularly where the file
needs to be run through `cp` (multiple direct mode files with same
content), there's no way to atomically replace the symlink with the
content.
Anyway, the bug turns out to be something that the watcher does right for
indirect mode, but not for direct mode. When it got an add event, it
checked to see if this was a new file, or one we've already added. In the
latter case, no add event was queued. But that means that only the rm event
is queued, and so it unstages the file.
Fixed by queueing an add event even when the file is already in git.
Tested by running hundreds of drops in a loop; file remained staged.
I would have sort of liked to put this in .gitattributes, but it seems
it does not support multi-word attribute values. Also, making this a single
config setting makes it easy to only parse the expression once.
A natural next step would be to make the assistant `git add` files that
are not annex.largefiles. OTOH, I don't think `git annex add` should
`git add` such files, because git-annex command line tools are
not in the business of wrapping git command line tools.
When a page is loaded, the javascript requests an notification url, and
does long polling on the url to be informed of changes. But if a change
occured before the notification url was requested, it would not be notified
of that change, and so the page display would not update.
I fixed this by *always* updating the page display after it gets
the notification url. This is extra work, but the overhead is not noticable
in the other overhead of loading a page.
(A nicer way would be to somehow record the version of a page initially
loaded, and then compare it with the current version when getting the
notification url, and only force an update if it's changed. But getting
the "version" of the different parts of the page that use long polling
is difficult.)
Like the old one, but does not mention which remotes are scanned.
I think this is less confusing, as it does not imply the remotes
were somehow accessed (which they are not; inaccessible remotes
can be scanned.)
If transferkey crashes or even fails to run, the TransferWatcher will not
see the transfer info file be created, so will not remove the transfer
from the list of active transfers. This causes the list to grow
continually, and all active transfers are displayed in the webapp. So, put
in a guard.
I assume that transferkey will not exit 0 while neglecting to clean up.
Rather than forking a git-annex transferkey only to have it fail,
just immediately record the failed transfer (so when the drive is plugged
in, the scan will retry it).
This may work around google talk's horrible presence handling, in which
clients often don't learn about other clients, at least when using the same
account. This way, every time we start a git push over xmpp, we'll waste
bandwidth asking clients to please try again to identify themselves.
Just before starting a transfer, do one last check that it's still
preferred content.
I was just doing this for uploads, as part of the smarter flood filling
bug, but realized it's also possible for a download that was preferred
content to change to not be before the download begins, so check that too.
Rather than wait a full second, which may be longer than needed, or too
short to get all the rename events, we start a mode where we wait 1/10th of
a second, and if there are Changes received, wait again. Basically we're
back in batch mode when this happens.
This cleaned up the code quite a bit; now the committer just looks at the
Change to see if it's a change that needs to have a transfer queued for it.
If I later want to add dropping keys for files that were removed, or
something like that, this should make it straightforward.
This also fixes a bug. In direct mode, moving a file out of an archive
directory failed to start a transfer to get its content. The problem
was that the file had not been committed to git yet, and so the transfer
code didn't want to touch it, since fileKey failed to get its key.
Only starting transfers after a commit avoids this problem.
This is not perfect, because on loss of connection, we do not currently
immediately detect it and stop the client. It has to time out, and then
the buddy list will clear.
The NetWatcher should detect disconnects too..
Noticed that, At startup or network reconnect, git push messages were sent,
often before presence info has been gathered, so were not sent to any
buddies.
To fix this, keep track of which buddies have seen such messages,
and when new presence is received from a buddy that has not yet seen it,
resend.
This is done only for push initiation messages, so very little data needs
to be stored.
This fixes the issue mentioned in the last commit.
Turns out just collecting UUID of clients behind a XMPP remote is
insufficient (although I should probably still do it for other reasons),
because a single remote repo might be connected via both XMPP and local
pairing. So a way is needed to know when a push was received from any
client using a given XMPP remote over XMPP, as opposed to via ssh.
Make manualPull send push requests over XMPP.
When reconnecting with remotes, those that are XMPP remotes cannot
immediately be pulled from and scanned, so instead maintain a set of
(probably) desynced remotes, and put XMPP remotes on it. (This set could be
used in other ways later, if we can detect we're out of sync with other
types of remotes.)
The merger handles detecting when a XMPP push is received from a desynced
remote, and triggers a scan then, if they have in fact diverged.
This has one known bug: A single XMPP remote can have multiple clients
behind it. When this happens, only the UUID of one client is recorded
as the UUID of the XMPP remote. Pushes from the other XMPP clients will not
trigger a scan. If the client whose UUID is expected responds to the push
request, it'll work, but when that client is offline, we're SOL.
Watcher wants to rewrite symlink to fix it. But in direct mode, the symlink
could be replaced at any time with file content that has finished being
transferred by some other process. So, just don't touch it.
FWIW, I audited the rest of the assistant for places where it removes
files, and the rest is ok. I have not audited the rest of git-annex.
assistant: Fix bug in direct mode that could occur when a symlink is moved
out of an archive directory, and resulted in the file not being set to
direct mode when it was transferred.
The bug was that the direct mode mapping was not up-to-date when the
transferrer finished. So, finding no direct mode place to store the object,
it was put into .git/annex in indirect mode.
To fix this, just make the watcher update the direct mode mapping to
include the new file before it starts the transfer. (Seems we don't need to
update it to remove the old file if the link was moved, because the direct
mode code will notice it's not present and the mapping gets updated for its
removal later.)
The reason this was a race, and was probably not seen often is because
the committer came along and updated the direct mode mapping as part of
adding the moved symlink. But when the file was sufficiently small or
the remote sufficiently fast, this could happen after the transfer
finished.
Looking through the git sources (documentation is unclear),
it seems commit doesn't ever trigger git-gc, mostly fetching and merging
seems to. I cannot easily override the setting in all those places, so
instead set gc.auto in git config when initializing a repository with
the assistant.
This does mean that the user cannot set gc.auto=0 and completely avoid
repacks, as the assistant does it daily. But, it only does it after there
are 100x the default number of loose objects, so this is probably not going
to be too annoying.
Pass subcommand as a regular param, which allows passing git parameters
like -c before it. This was already done in the pipeing set of functions,
but not the command running set.
A transfer is queued, but if the file has already been transferred to the
remote before, the transfer is skipped. In this case, it needs to perform
any actions it would normally take after finishing the transfer, like
dropping the local object.
This cannot completely guard against a runaway log event, and only runs
every hour anyway, but it should avoid most problems with very
long-running, active assistants using up too much space.
Refactored annex link code into nice clean new library.
Audited and dealt with calls to createSymbolicLink.
Remaining calls are all safe, because:
Annex/Link.hs: ( liftIO $ createSymbolicLink linktarget file
only when core.symlinks=true
Assistant/WebApp/Configurators/Local.hs: createSymbolicLink link link
test if symlinks can be made
Command/Fix.hs: liftIO $ createSymbolicLink link file
command only works in indirect mode
Command/FromKey.hs: liftIO $ createSymbolicLink link file
command only works in indirect mode
Command/Indirect.hs: liftIO $ createSymbolicLink l f
refuses to run if core.symlinks=false
Init.hs: createSymbolicLink f f2
test if symlinks can be made
Remote/Directory.hs: go [file] = catchBoolIO $ createSymbolicLink file f >> return True
fast key linking; catches failure to make symlink and falls back to copy
Remote/Git.hs: liftIO $ catchBoolIO $ createSymbolicLink loc file >> return True
ditto
Upgrade/V1.hs: liftIO $ createSymbolicLink link f
v1 repos could not be on a filesystem w/o symlinks
Audited and dealt with calls to readSymbolicLink.
Remaining calls are all safe, because:
Annex/Link.hs: ( liftIO $ catchMaybeIO $ readSymbolicLink file
only when core.symlinks=true
Assistant/Threads/Watcher.hs: ifM ((==) (Just link) <$> liftIO (catchMaybeIO $ readSymbolicLink file))
code that fixes real symlinks when inotify sees them
It's ok to not fix psdueo-symlinks.
Assistant/Threads/Watcher.hs: mlink <- liftIO (catchMaybeIO $ readSymbolicLink file)
ditto
Command/Fix.hs: stopUnless ((/=) (Just link) <$> liftIO (catchMaybeIO $ readSymbolicLink file)) $ do
command only works in indirect mode
Upgrade/V1.hs: getsymlink = takeFileName <$> readSymbolicLink file
v1 repos could not be on a filesystem w/o symlinks
Audited and dealt with calls to isSymbolicLink.
(Typically used with getSymbolicLinkStatus, but that is just used because
getFileStatus is not as robust; it also works on pseudolinks.)
Remaining calls are all safe, because:
Assistant/Threads/SanityChecker.hs: | isSymbolicLink s -> addsymlink file ms
only handles staging of symlinks that were somehow not staged
(might need to be updated to support pseudolinks, but this is
only a belt-and-suspenders check anyway, and I've never seen the code run)
Command/Add.hs: if isSymbolicLink s || not (isRegularFile s)
avoids adding symlinks to the annex, so not relevant
Command/Indirect.hs: | isSymbolicLink s -> void $ flip whenAnnexed f $
only allowed on systems that support symlinks
Command/Indirect.hs: whenM (liftIO $ not . isSymbolicLink <$> getSymbolicLinkStatus f) $ do
ditto
Seek.hs:notSymlink f = liftIO $ not . isSymbolicLink <$> getSymbolicLinkStatus f
used to find unlocked files, only relevant in indirect mode
Utility/FSEvents.hs: | Files.isSymbolicLink s = runhook addSymlinkHook $ Just s
Utility/FSEvents.hs: | Files.isSymbolicLink s ->
Utility/INotify.hs: | Files.isSymbolicLink s ->
Utility/INotify.hs: checkfiletype Files.isSymbolicLink addSymlinkHook f
Utility/Kqueue.hs: | Files.isSymbolicLink s = callhook addSymlinkHook (Just s) change
all above are lower-level, not relevant
Audited and dealt with calls to isSymLink.
Remaining calls are all safe, because:
Annex/Direct.hs: | isSymLink (getmode item) =
This is looking at git diff-tree objects, not files on disk
Command/Unused.hs: | isSymLink (LsTree.mode l) = do
This is looking at git ls-tree, not file on disk
Utility/FileMode.hs:isSymLink :: FileMode -> Bool
Utility/FileMode.hs:isSymLink = checkMode symbolicLinkMode
low-level
Done!!
git annex init probes for crippled filesystems, and sets direct mode, as
well as `annex.crippledfilesystem`.
Avoid manipulating permissions of files on crippled filesystems.
That would likely cause an exception to be thrown.
Very basic support in Command.Add for cripped filesystems; avoids the lock
down entirely since doing it needs both permissions and hard links.
Will make this better soon.
Making the pre-commit hook look at git diff-index to find changed direct
mode files and update the mappings works pretty well.
One case where it does not work is when a file is git annex added, and then
git rmed, and then this is committed. That's a no-op commit, so the hook
probably doesn't even run, and it certianly never notices that the file
was deleted, so the mapping will still have the original filename in it.
For this and other reasons, it's important that the mappings still be
treated as possibly inconsistent.
Also, the assistant now allows the pre-commit hook to run when in direct
mode, so the mappings also get updated there.
New setting, can be used to disable autocommit of changed files by the
assistant, while it still does data syncing and other tasks.
Also wired into webapp UI
It used to not log to daemon.log when a repository was first created, and
when starting the webapp. Now both do. Redirecting stdout and stderr to the
log is tricky when starting the webapp, because the web browser may want to
communicate with the user. (Either a console web browser, or web.browser = echo)
This is handled by restoring the original fds when running the browser.
since some systems may have configuration problems or other issues that
prevent web browsers from connecting to the right localhost IP for the
webapp.
Tested on both ipv4 and ipv6 localhost. Url for the latter looks like:
http://[::1]:50676
The expensive scan uses lookupFile, but in direct mode, that doesn't work
for files that are present. So the scan was not finding things that are
present that need to be uploaded. (It did find things not present that
needed to be downloaded.)
Now lookupFile also works in direct mode. Note that it still prefers
symlinks on disk to info committed to git, in direct mode. This is
necessary to make things like Assistant.Threads.Watcher.onAddSymlink
work correctly, when given a new symlink not yet checked into git (or
replacing a file checked into git).
Would like to also have restart UI, but that's rather harder to do,
seems it'd need to start another copy of the webapp, and redirect the
browser to its new url, but running two assistants in the same repo at
the same time isn't good.
Now there's a Config type, that's extracted from the git config at startup.
Note that laziness means that individual config values are only looked up
and parsed on demand, and so we get implicit memoization for all of them.
So this is not only prettier and more type safe, it optimises several
places that didn't have explicit memoization before. As well as getting rid
of the ugly explicit memoization code.
Not yet done for annex.<remote>.* configuration settings.
When a file is changed in direct mode, the old content is probably lost
(at least from the local repo), and bookeeping needs to be updated to
reflect this.
Also, synthetic add events are generated at assistant startup, so
make it detect when the file has not really changed, and avoid re-adding
it.
This does add the overhead of querying the runing git cat-file for the
key that's recorded in git for the file, each time a file is added or
modified in direct mode.
git add --update cannot be used, because it'll stage typechanged direct
mode files. Intead, use ls-files to find deleted files, and stage them
ourselves.
It seems that no commit was made before when the scan staged deleted files.
(Probably masked since if files were added, a commit happened then..)
Now that I'm doing the staging, I was also able to fix that bug.
This allows it to use Build.SysConfig to always install the programs
configure detected. Amoung other fixes, this ensures the right uuid
generator and checksum programs are installed.
I also cleaned up the handling of lsof's path; configure now checks for
it in PATH, but falls back to looking for it in sbin directories.
* get/copy --auto: Transfer data even if it would exceed numcopies,
when preferred content settings want it.
* drop --auto: Fix dropping content when there are no preferred content
settings.
Noticed that when pairing, sometimes both sides start to push, and the other
side sends a PushRequest, and the two deadlock, neither doing anything.
(Timeout eventually breaks this.) So, let both run at the same time.
This should help prevent git-annex clients receiving messages that
were intended for normal clients they're sharing the account with.
Changed XMPP protocol use to always send chat messages directed at the
specific client, as the negative priority blocks less directed messages.
It might even work, although nothing yet triggers XMPP pushes.
Also added a set of deferred push messages. Only one push can run at a
time, and unrelated push messages get deferred. The set will never grow
very large, because it only puts two types of messages in there, that
can only vary in the client doing the push.
