README

** THIS PROJECT IS DEFUNCT **

It remains here as a reminder of what I did.

It was a nice idea and it does achieve an awesome compression ratio, but it is
very time consuming `bup` beats it for convenience. Unfortunately, git doesn't
generate great packs, so frequent repacking is needed in order to achieve good
delta compression. After a month of hourly backups, this takes hours.

Keeping the world files in the same repository as the configuration also proved
to be a mistake, as all git operations (status, add, etc) have to run the files
through the smudge filter. This is painfully slow.

If I was doing it again, I'd recommend trying out `bup` and maybe try using it
as a backend for `git-annex`.


git-minecraft-smudge
--------------------

Abusing git's filter mechanism for fun and profit.

note: This is a crazy thing to do and should be considered untested.

You have been warned.

Purpose
-------

This results in a drastic space saving when using git to track minecraft anvil
files. It works by decompressing minecraft's chunk data so that git's delta
compression can work more effectively on it.

Why?
----

I want to have backups for two purposes, one to see how it evolves over a long
period of time, and another in case we have a severe problem (nuke going off)
which we need to fix.

Result
------
For 10 saves with a significant amount of stuff done to them, the resulting git
repository was only 7% larger than the final save itself. A regular `git gc` is
needed.

Usage
-----

In your `.gitconfig` (doesn't cause anything by itself):

	[filter "minecraft-anvil"]
		clean = git-minecraft-smudge clean -
		smudge = git-minecraft-smudge smudge -

and in your `.gitattributes` in your world folder or higher:

	*.mca minecraft-anvil

note: this renders the repository unusable without `git-minecraft-smudge`.


Implementation details
---------------------

Unfortunately java's zlib implementation does something different to go's,
which I wasn't able to figure out. So instead I call upon java just to do the
compression.

I also wanted to just have one binary named `git-minecraft-smudge` that did
everything, so the `Makefile` embeds the `.jar` into the binary which is
unpacked at runtime.

Notes
-----

This seriously slows down many git operations including `status` `add` and
`commit`, since it must put all files with modified timestamps through the
`clean` phase, which is time consuming since it always verifies that it can
repack the file to exactly the same contents.