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all easy cases done

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bup can't do it after all, because removeKey deletes the git branch. And
the rest seem too hard to tackle today.
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Joey Hess 2020-06-26 14:24:48 -04:00
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38
doc/todo/lockContent_for_special_remotes.mdwn
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@ -1,13 +1,24 @@
Currently only Remote.Git implements lockContent. It seems like some other
special remotes can lock content though:
Support lockContent in more special remotes. This allows dropping
content from a special remote when the only copies are in other special
remotes.
(All the easy ones, eg read-only special remotes, are implemented already.)
* bup and git-lfs and tahoe can't drop content, so content is implicitly locked
* S3 has an object lock feature, I don't know if it would be usable for
this, but woth investigating.
* adb could use some shell trick perhaps
* It might be possible for an external remote to lock content, but it would
be a tricky extension to the protocol, since lockContent needs to keep it
locked while running another action.
locked while running another action. There would need to be separate
actions for locking and unlocking.
If this were implemented in git-annex, and some special remote program
didn't used to support it, and implemented REMOVE w/o checking a lock,
then making that program support lockContent would run the risk
of a misture of the old and new version being in use for the same remote,
which could result in data loss.
To avoid that, the author of the special remote would need to either
a) always do lock checking from the beginning or
b) wait long enough or document well enough to be sure that situation
never happens.
* directory could use fcntl locking
@ -22,3 +33,16 @@ special remotes can lock content though:
locking, with various failure modes. And unlike a git-annex repo,
there's nowhere in a directory special remote to record information about
locking problems with it. Getting this right seems hard..
* S3 has an object lock feature, I don't know if it would be usable for
this.
It would need a transition, with dropKey first failing when the object
lock was in place, and then once that git-annex was in use everywhere,
lockContent setting the object lock.
(S3 with versioning=yes already supports lockContent.)
* adb could use some shell trick perhaps.. But it would depend on doing
locking in /sdcard, which seems likely to be a massive ball of POSIX
incompliance and pain.