Now available on mips, mipsel, but temporarily removed armel since build is
failing there.
If armel would just get caught up, I could remove the per-arch specs
entirely.
Maybe time to turn maint of this over to richih?
Decided it's too scary to make v6 unlocked files have 1 copy by default,
but that should be available to those who need it. This is consistent with
git-annex not dropping unused content without --force, etc.
* Added annex.thin setting, which makes unlocked files in v6 repositories
be hard linked to their content, instead of a copy. This saves disk
space but means any modification of an unlocked file will lose the local
(and possibly only) copy of the old version.
* Enable annex.thin by default on upgrade from direct mode to v6, since
direct mode made the same tradeoff.
* fix: Adjusts unlocked files as configured by annex.thin.
This optimisation was not necessary, and didn't work for v6 unlocked files.
Typically only a small number of files will be changed by a commit, so just
catKey them all.
In copyFromRemote, it used to check isDirect, but that was not needed;
the remote is sending the file, so it doesn't matter if the local,
receiving repository is in direct mode or not. And, since the content is not
present, yet, it's certianly not unlocked. Note that, the remote may indeed
be sending an unlocked file, but sendkey uses sendAnnex, which will detect
if the file is modified before or during transfer, and will exit nonzero,
aborting the upload. So, the receiver doesn't need any checks.
In copyToRemote, it forces recvkey to verify content whenever it's being
sent from a v6 repository. recvkey is almost always going to verify content
anyway, unless annex.verify is not set. So, this doesn't make it any more
expensive, except for in that unusual configuration. The alternative would
be to change the recvkey interface, so that the sender checks afterwards if
what it was sending changed, and the receiver then throws out the bad
transfer. That would be less expensive for the reciever, as it would not
need to do a checksum verification. But, it would mean another network
round trip, and since rsync closes the connection, it would need to open
another ssh connection to do this. Even with connction caching, that would
add latency to uploads. It would also complicate the interface, especially
because an older git-annex-shell would not have the new interface
available. For these reasons, I prefer punting on that at this time, and
instead someone might set annex.verify=false and be unhappy that it still
verifies..
(One other gotcha not dealt with is that a v5 repo could be upgraded to v6
while an upload is in progress, and a file unlocked and modified.)
(Also, I double-checked Remote.GCrypt's calls to rsyncParamsRemote, and
they're fine. When a file is being uploaded to gcrypt, or any other special
repository, it is mediated by sendAnnex, so changes will be detected at
that level and the special remote implementation doesn't need to worry
about them.)
The direct flag is also set when sending unlocked content, to support old
versions of git-annex-shell. At some point, the direct flag will be
removed, and only the unlocked flag will be used.
Writes are optimised by queueing up multiple writes when possible.
The queue is flushed after the Annex monad action finishes. That makes it
happen on program termination, and also whenever a nested Annex monad action
finishes.
Reads are optimised by checking once (per AnnexState) if the database
exists. If the database doesn't exist yet, all reads return mempty.
Reads also cause queued writes to be flushed, so reads will always be
consistent with writes (as long as they're made inside the same Annex monad).
A future optimisation path would be to determine when that's not necessary,
which is probably most of the time, and avoid flushing unncessarily.
Design notes for this commit:
- separate reads from writes
- reuse a handle which is left open until program
exit or until the MVar goes out of scope (and autoclosed then)
- writes are queued
- queue is flushed periodically
- immediate queue flush before any read
- auto-flush queue when database handle is garbage collected
- flush queue on exit from Annex monad
(Note that this may happen repeatedly for a single database connection;
or a connection may be reused for multiple Annex monad actions,
possibly even concurrent ones.)
- if database does not exist (or is empty) the handle
is not opened by reads; reads instead return empty results
- writes open the handle if it was not open previously
