git-annex/doc/upgrades.mdwn

[[!toc levels=3]]

# Software upgrades

Upgrading the code base of git-annex will be done differently depending on
your [[install]] method. For most distribution-based packages, it is
handled by the package management software.

For the standalone distribution, the [[git-annex-webapp]](1) will ask the
user for confirmation when it detects a new version. Once that is
confirmed, or if `annex.autoupgrade` is enabled (see the [[git-annex]](1)
manpage) the assistant will start the upgrade. The upgrade process is
fairly simple: the assistant will move the `git-annex.linux` directory out
of the way and replace it with the new version, then re-execute itself. It
therefore needs write access to the parent directory of the
`git-annex.linux` directory.

Note that "upgrading" from a distribution-based package to the
[[install/Linux_standalone/]] version may cause weird problems, as an
unexpected version of git-annex (e.g. the old one from packages) may be
ran.

# Repository upgrades

Occasionally improvements 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 commitment 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.

git-annex will notice if it is run in a repository that
needs an upgrade, and either automatically upgrade it or
refuse to do anything. To upgrade, use the "git annex upgrade" command.

To prevent automatic upgrades in a repository, run:
`git config annex.autoupgraderepository false`

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.

The upgrade process needs to write to the repository. If the original
repository cannot be written to (due to eg being on readonly media),
the upgrade would need to be run in a copy of the repository.

The upgrade events, so far:

## v6 -> v7 (git-annex version 7.x)

v6 repositories are automatically upgraded to v7.

The only difference between v6 and v7 is that some additional git hooks
were added in v7. See below for details about what's new in v6/v7.

## v5 -> v6 (git-annex version 6.x)

v5 repositories are automatically upgraded to v6.

A v6 git-annex repository can have some files locked while other files are
unlocked, and all git and git-annex commands can be used on both locked and
unlocked files. It's a good idea to make sure that all users of the
repository have upgraded git-annex and upgraded their repositories
to the new version before starting to use this feature, since old
versions of git-annex will ignore the new unlocked files.

Direct mode repositories are upgraded to instead use the new 
[[adjusted branches feature|git-annex-adjust]], which transparently unlocks
all locked files in the local repository.

The behavior of some commands changes in an upgraded repository:

* `git add` will add files to the annex, rather than adding them directly
   to the git repository. To cause some files to be added directly
   to git, you can configure `annex.largefiles`. For example:

   	`git config annex.largefiles "largerthan=100kb and not (include=*.c or include=*.h)"`

* `git annex unlock` and `git annex lock` change how the pointer to 
  the annexed content is stored in git. If you commit the change,
  that will impact all clones of the repository. This means all clones of the
  repository will need to run at least v6 to correctly synchronise.

There is also a new `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. This is automatically
enabled when upgrading a direct mode repository, since direct mode made the
same tradeoff.

See [[tips/unlocked_files/]] for more details about locked files and thin
mode.

## v4 -> v5 (git-annex version 5.x)

The upgrade from v4 to v5 is handled
automatically, and only affects [[direct mode]] repositories.

This upgrade involves changing direct mode repositories to operate with
core.bare=true.

## v3 -> v4 (git-annex version 4.x)

v4 was only used for [[direct_mode]], to ensure that a version of git-annex
that understands direct mode was used with a direct mode repository. 

## v2 -> v3 (git-annex version 3.x)

Involved moving the .git-annex/ directory into a separate git-annex branch.

After this upgrade, you should make sure you include the git-annex branch
when git pushing and pulling.

### tips for this upgrade

This upgrade is easier (and faster!) than the previous upgrades.
You don't need to upgrade every repository at once; it's sufficient
to upgrade each repository only when you next use it.
	
Example upgrade process:

	cd localrepo
	git pull
	git annex upgrade
	git commit -m "upgrade v2 to v3"
	git gc

## v1 -> v2 (git-annex 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.

Previously, files added to the SHA [[backends]] did not have their file
size tracked, while files added to the WORM backend did. Files added to
the SHA backends after the conversion will have their file size tracked,
and that information will be used by git-annex for disk free space checking.
To ensure that information is available for all your annexed files, see
[[upgrades/SHA_size]].

### tips for this upgrade

This 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.

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.

Example upgrade process:

	cd localrepo
	git pull
	git annex upgrade
	git commit -m "upgrade v1 to v2"
	git push

	ssh remote
	cd remoterepo
	git pull
	git annex upgrade
	...

## v0 -> v1 (git-annex 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.

Before doing this upgrade, set annex.version:

	git config annex.version 0