Creating a patch file
Creating a patch file is really easy. First, check out the most recent version of the code from Subversion using the ‘checkout’ command.
Make your changes. Then, in the root the project run the following command. It will store the patch file in your home directory. Make sure to give it meaningful filename.
svn diff > ~/fix_bug.diff
The file has the .diff extention, which stands for differences. This extension is recognized by many text editors and enables ’syntax highlighting’ automatically. (Give it a try with TextMate and you’ll know what I mean.) You can send the diff-file to the author of the project by email, or you can create a ticket in Trac and add it as an attachment. The author will review the changes you made and possibly apply them to the source.
Applying a patch
You should never apply patches from any person other than your development team without first reading through the changes, apply them locally and test your application and then commit them. Patches can not only include bug fixes, but also alterations to create back doors or add other exploits to your code.
Always read through a patch before applying it!
When you are sure the patch will bring no harm to you, your application or your customers, go ahead an apply it to your working copy. Here, I assume that you downloaded the patch file we previously generated, and placed it in your home directory. In the root of your application now run:
patch -p0 -i ~/fix_bug.diff
This will apply all the changes in the patch to your source. The -p0 option makes sure that all files can be found correctly (this has to do with something called ‘zero directories’, I won’t get into that right now). The -i option tells ‘patch’ what to use as input, in this case the ‘fix_bug.diff’ file in your home directory.
With the code changes in place, run your tests and make sure everything works as expected. If it does, commit your changes.