[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2880: Magic-folder needlessly creates ".backup" files after restart

[Tahoe-LAFS]

#2880: Magic-folder needlessly creates ".backup" files after restart
--------------------------+---------------------------
 Reporter:  cypher        |          Owner:
     Type:  defect        |         Status:  new
 Priority:  normal        |      Milestone:  undecided
Component:  unknown       |        Version:  1.12.1
 Keywords:  magic-folder  |  Launchpad Bug:
--------------------------+---------------------------
 After placing a single file into a local magic-folder directory, a
 subsequent `restart` of the tahoe client will a create ".backup" copy of
 that file that is bit-for-bit identical to the original despite the fact
 that no changes have been made to the file on the "grid"-side to warrant
 it. As a demonstration:

 {{{
 dev ~ % cp cat.jpg Magic-Folder
 dev ~ % ls -al Magic-Folder
 total 116K
 drwxr-xr-x  2 user user 4.0K Jun 21 14:48 .
 drwxr-xr-x 57 user user 4.0K Jun 21 14:28 ..
 -rw-r--r--  1 user user 107K Jun 21 14:48 cat.jpg
 dev ~ % tahoe restart
 STOPPING '/home/user/.tahoe'
 process 2592 is dead
 STARTING '/home/user/.tahoe'
 starting node in '/home/user/.tahoe'
 dev ~ % ls -al Magic-Folder
 total 224K
 drwxr-xr-x  2 user user 4.0K Jun 21 14:49 .
 drwxr-xr-x 57 user user 4.0K Jun 21 14:28 ..
 -rwx------  1 user user 107K Jun 21 14:48 cat.jpg
 -rw-r--r--  1 user user 107K Jun 21 14:48 cat.jpg.backup
 dev ~ % sha256sum Magic-Folder/cat.jpg*
 7be4d6e0365150ef684545e29de088ed9419398f473d43c3c983afce6e9fdc72  Magic-
 Folder/cat.jpg
 7be4d6e0365150ef684545e29de088ed9419398f473d43c3c983afce6e9fdc72  Magic-
 Folder/cat.jpg.backup
 }}}

 As far as I can tell, this occurs consistently with every run, thereby
 leading to the situation when, under ordinary usage, a user will
 eventually have a ".backup" duplicate for every file within their local
 magic-folder. This is undesirable not only due to the wasted disk space,
 but because the multititude of backup copies can impede the user's ability
 to distinguish a meaningful backup copy (i.e., one produced as a result of
 another's magic-folder member's action) from all the others.

 Ideally, these files should only be generated under meaningful
 circumstances or when otherwise beneficial to the user (for example, when
 another magic-folder member overwrites or deletes the local user's copy).

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2880>
Tahoe-LAFS <https://Tahoe-LAFS.org>
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