Xcode .gitignore template

The three rules at the end of this template do the interesting work. *.xcodeproj/* ignores the contents of the project bundle, then two negations bring back project.pbxproj and the xcshareddata directory. The bundle is a directory pretending to be a file, and inside it sit both the project definition everyone needs and the per developer state nobody else wants.

project.pbxproj is the project definition: every file reference, build phase and target setting. It must be tracked. It is also notorious for merge conflicts, because it is a single large file that the editor rewrites in full and that changes whenever anyone adds a file. That is a real cost of the format rather than something an ignore file can fix.

xcshareddata holds shared schemes, which describe how to build, test and run each target. Marking a scheme as shared moves it from your user data into that directory, which is the mechanism for sharing a run configuration with the team. The xcuserdata rule covers the other side: breakpoints, window layout and unshared schemes, all of which are yours alone.

DerivedData is the build cache: module caches, indexes, intermediate products and build logs. It is normally outside the project directory, but a project configured to use a relative path will produce it inside, and it is large and entirely regenerated.

Pods is the dependency manager's installed sources directory. Whether to commit it is a genuine argument: committing gives you reproducible builds without a network fetch and a much larger repository, while ignoring it relies on the lockfile plus the dependency sources still being available. This template takes the ignore side, which is the more common choice now.