The problem
===========

[Calibre](http://calibre-ebook.com/) is a ebook manager that is
available in [debian](http://packages.debian.org/sid/calibre). I use
it to maintain my library, but also to dowload every day an epub
version of a French newspaper and then put it on my kobo.

Configuring git annex for this
==============================

I wanted to use git-annex, so

    $ git init
    $ git annex init "some useful name"

But I don't want every thing in annex, because Calibre use some text
file to save some metadata, so I used:

    $ git config annex.largefiles "include=* exclude=*.opf exclude=*.json"

then lets add everything

    $ git annex add *
    $ git add *
    $ git commit -m "first commit"

Calibre need read and write access on the its database, so let unlock it:

    $ git annex unlock metadata.db

On my other computer I only need to do

    $ git clone $user@$host:Calibre\ library
    $ cd Calibre\ library
    $ git annex init "another useful name"
    $ git annex get .
    $ git annex unlock metadata.db

The problem is that every time you will `git annex sync`, git annex
will lock again the metadata.db, so lets unlock it automatically. I
use git hooks, in `.git/hooks/post-commit` I have

    #!/bin/bash

    git annex edit metadata.db

don't forget to make this file executable

    $ chmod a+x .git/hooks/post-commit

Day to day operation
====================

    $ git annex add .

Will put new file into the annex

    $ git add .

Will take care of the files that should no go into annex

    $ git annex sync

Will make the repositories exchange informations about all this, and
make remote change local

    $ git annex get .

Will make remote book locally available

Merge conflict
--------------
You should not run calibre on the two computer simultaneously, or
without syncing before it. If you do, you will have a conflict that
git-annex will automatically *solve* by rename both of the file.

You can then either:

 - Choose one. If no books have been changed or added on one of the
   computer, to use the other `metadata.db` will not make you loose
   any information
 - rebuild it. `calibredb restore_database` won't do it, but will tell
   you how to do it.

Checking the library
--------------------
You can use `calibredb check_library` to check you library is
correct. If you use git for it, it will always tell you that it is not
correct: there is this author ".git" it doesn't know about. Just don't
care about it.

Maybe this can be solved by using `vcsh` but apparently
`vcsh`+`git annex` it not well tested yet.

Automatic stuff
---------------
I use `mr` to automatically run all this, but some config could be
done (I believe) to have `git annex copy --auto` do what it should.

There are also the git annex assistant for this kind of automatic
synchronizations of contents, but I don't know if my automatic
unlocking of one file will break this.

It might be interesting to find someway to unlock and lock the library
only when running calibre, a simple script to launch calibre will do
that. Note that each time you will lock and unlock, you will have a
new commit in git.

Another solution
===================
You could also use direct mode in place of the auto unlock feature

    git annex direct

The remove the `post-commit` git hook (or do not add it). Its a
simpler solution, but remember that interaction between git annex direct
repositories and plain git are complex and sometimes downright dangerous. See [[direct mode]] for details.

In particular, do *not* called `git add *` in the above steps, as that will commit all books into git.