Swift .gitignore template

.build is where the package manager puts everything it compiles, including every dependency it fetched. Packages is the older checkout directory from the same tool. Both are restored from the manifest, both contain absolute paths to the machine that built them, and both grow large enough that a committed copy dominates the repository.

Package.resolved is the lockfile, and ignoring it is the choice this template makes on your behalf. It records the exact commit of every dependency the resolver settled on. For an application that you ship, that pinning is the whole point, and the file belongs in the repository so that a colleague and your CI build the same thing you did. For a library it matters far less, since anything depending on you resolves independently.

xcuserdata is per developer state: breakpoints, window layout, which schemes you marked shared. It sits inside the project bundle, so it is easy to commit by accident, and once committed it produces a conflict every time two people open the project. The pbxuser, mode1v3, mode2v3 and perspectivev3 rules are older versions of the same idea, each paired with a negation that keeps the default variant.

DerivedData is the shared build cache Xcode keeps, holding indexes, module caches and intermediate products. *.hmap files are header maps generated during the build. None of it is portable and all of it is rebuilt on demand, usually within one clean build.

The distribution rules cover *.ipa, the packaged application archive, and *.dSYM plus *.dSYM.zip, the debug symbol bundles that let you symbolicate a crash report. Symbol bundles are release artefacts that belong with the build that produced them, in a crash reporting service or an artefact store rather than in git.