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+I am not sure this is the case, but from first-hand experience, it
+sure looks like you can't turn on v7 (or really v6, actually) on a
+single git worktree. For example, if I have my `pictures` repository
+on `curie` and turn on v7, `angela` will *also* need to run `git annex
+upgrade` on their worktree otherwise git-annex
+(e.g. 6.20180913-1~bpo9+1 on Debian stretch) will be really confused:
+
+    anarcat@angela:calendes$ less calendrier/calendes.pdf
+    /annex/objects/SHA256E-s117451415--8d7d8366094a63c54bef99b5cd2e2b5187092f834d8bf7002e1d5fdceb38a710.pdf
+    anarcat@angela:calendes$ git annex get calendrier/calendes.pdf
+    anarcat@angela:calendes$ git annex whereis calendrier/calendes.pdf
+    anarcat@angela:calendes$ # OMG WHERE ARE MY FILES! /me flails wildly
+
+:)
+
+It seems to me there should be a warning in the [[upgrades]] page
+about this. I would have done so myself, but I'm not sure (like in my
+last bug report) if I am doing things right.
+
+In this case, this repository was already present (v5, indirect mode)
+on both machines. I upgraded (using `git annex upgrade`) the
+repository on curie (7.20181121 Debian buster) which went well.
+
+(Then I messed around with that thumb drive, which led to
+[[bugs/v7_fails_to_fetch_files_on_FAT_filesystem]], but probably
+unrelated here.)
+
+Then i powered on my laptop (`angela`) and saw the above. I would have
+expected it to either upgrade automatically or warn me about the
+repository inconsistency. Of failing that, the upgrades page should at
+least warn us this is a "system-wide" (how do we call that?) change...
+
+The workaround is to run `git annex upgrade` on that other repo, of
+course, but if the source repo was also upgraded, it might be
+difficult to sync files, as you will see that warning:
+
+    $ git annex get
+    get calendrier/calendes.pdf (from sneakernet...) 
+    Repository version 7 is not supported. Upgrade git-annex.
+
+Considering there's no backport of 7.x in Debian stretch, it makes the
+upgrade path rather delicate... Is there a way to "downgrade" that
+sneakernet repo? :) (Thankfully, the main server still runs v5 so the
+files are still accessible from stretch....) -- [[anarcat]]