Magento 1 Update - How to

Rico Neitzel told me back in the days, that during Magento updates files gets deleted, therefore it is a bad idea, therefore you want to run a patch (not the ones from Magento, but a patch between the versions) over your Magento installation.

After fiddeling around for a while it is a good idea to document, what I have just done (I updated from 1.9.2.2 to 1.9.3.3):

1. Get a trusted git repository with all Magento versions you need, I can recommend https://github.com/OpenMage/magento-mirror

2. Clone it

    git clone https://github.com/OpenMage/magento-mirror.git
   

3. Make sure your current installation is free of core hacks and all files exists which might get patched

    magento-mirror$ git checkout 1.9.2.2 (old version)
    production$  rsync --progress -v -r ../magento-mirror/* .
   

4. You might have now too much files - either you have them already in your gitignore - if not, time to add them.

5. Create a patch file (diff-index is needed for binary patches)

    magento-mirror$ git checkout 1.9.3.3 (new version)
    magento-mirror$ git diff-index 1.9.2.2 --binary > patch.patch
   

6. Apply the patch

    production$ git apply --binary ../magento-mirror/patch.patch
   

7. Now you have a working copy with all the changes. You can review them, commit them, etc.