Free File Comparison Software
I maintain several websites all of which make use of WordPress for managing and publishing content. WordPress is quite feature-rich out of the box, but it becomes even more powerful when you install some of the hundreds of add-ons that have been created for it. And when add-ons don't solve a particular need, there's always the possibility of changing the code of the WordPress core. The problem, however, with something that can be customized is that I sometimes lose track of my changes and forget to apply them to all of my sites. Fortunately, for me, there are file comparison tools that make tracking down differences easy.
WinMerge has long been my favorite tool for comparing files and merging differences. It is able to compare folders as well as making it easy to find what changes have been made to one of my websites, but not to another. File filters make it easy to keep the process targeted at PHP files so that I can ignore other file types such as images. In addition, WinMerge is portable so it can come with me on a USB drive (unlike the DiffMerge tool I wrote about below).
Most recently I tried another file comparison tool from a company whose other software I like. This tool, DiffMerge, promised to fill in the gaps of other tools and so I was quite interested in giving it a try. The good news is that DiffMerge does seem to include some useful improvements over WinMerge such as a folder filter that allows me to exclude cache and backup folders from comparisons. The bad news is that it falls short on the merging side because for some reason DiffMerge assumes that changes will always move from "left to right". When comparing old and new files of the same project this restriction is fine. When comparing files across projects i.e. different websites such a restriction is a hassle since it requires additional steps to synchronize two files that have both been modified.
In all likelihood I will stick with WinMerge. I place a big premium on applications that are portable even when it means missing out on a feature or two. If we're lucky, these two software writers will compete with each other to make even better versions with features none of us even know are missing!