git-annex/doc/upgrades.mdwn

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Occasionally improvments are made to how git-annex stores its data,
that require an upgrade process to convert repositories made with an older
version to be used by a newer version. It's annoying, it should happen
rarely, but sometimes, it's worth it.
There's a committment that git-annex will always support upgrades from all
past versions. After all, you may have offline drives from an earlier
git-annex, and might want to use them with a newer git-annex.
## Upgrade process
git-annex will notice if it is run in a repository that
needs an upgrade, and refuse to do anything. To upgrade,
use the "git annex upgrade" command. The upgrade can tend
to take a while, if you have a lot of files.
Each clone of a repository should be individually upgraded.
Until a repository's remotes have been upgraded, git-annex
will refuse to communicate with them.
Generally, start by upgrading one repository, and then you can commit
the changes git-annex staged during upgrade, and push them out to other
repositories. And then upgrade those other repositories. Doing it this
way avoids git-annex doing some duplicate work during the upgrade.
The upgrade process is guaranteed to be conflict-free. Unless you
already have git conflicts in your repository or between repositories.
Upgrading a repository with conflicts is not recommended; resolve the
conflicts first before upgrading git-annex.
Example upgrade process:
cd localrepo
git pull
git annex upgrade
(Upgrading object directory layout v1 to v2...)
git commit -m "upgrade v1 to v2"
git push
ssh remote
cd remoterepo
git pull
git annex upgrade
...
## Upgrade events, so far
### v1 -> v2 (git-annex version 0.23 to version 0.20110316)
Involved adding hashing to .git/annex/ and changing the names of all keys.
Symlinks changed.
Also, hashing was added to location log files in .git-annex/.
And .gitattributes needed to have another line added to it.
### v0 -> v1 (git-annex version 0.03 to version 0.04)
Involved a reorganisation of the layout of .git/annex/. Symlinks changed.
Handled more or less transparently, although git-annex was just 2 weeks
old at the time, and had few users other than Joey.
This upgrade is believed to still be supported, but has not been tested
lately.