Git Sparse Checkout: Pattern Sets and Cone Mode

changing the sparse-checkout patterns in cone mode, Git will inspect each tracked directory that is not within the sparse-checkout cone to see if it contains any untracked files. If all of those files are ignored due to the `.gitignore` patterns, then the directory will be deleted. If any of the untracked files within that directory is not ignored, then no deletions will occur within that directory and a warning message will appear. If these files are important, then reset your sparse-checkout definition so they are included, use `git add` and `git commit` to store them, then remove any remaining files manually to ensure Git can behave optimally. See also the "Internals -- Cone Pattern Set" section to learn how the directories are transformed under the hood into a subset of the Full Pattern Set of sparse-checkout. INTERNALS -- FULL PATTERN SET ----------------------------- The full pattern set allows for arbitrary pattern matches and complicated inclusion/exclusion rules. These can result in O(N*M) pattern matches when updating the index, where N is the number of patterns and M is the number of paths in the index. To combat this performance issue, a more restricted pattern set is allowed when `core.sparseCheckoutCone` is enabled. The sparse-checkout file uses the same syntax as `.gitignore` files; see linkgit:gitignore[5] for details. Here, though, the patterns are usually being used to select which files to include rather than which files to exclude. (However, it can get a bit confusing since gitignore-style patterns have negations defined by patterns which begin with a '!', so you can also select files to _not_ include.) For example, to select everything, and then to remove the file `unwanted` (so that every file will appear in your working tree except the file named `unwanted`): git sparse-checkout set --no-cone '/*' '!unwanted' These patterns are just placed into the `$GIT_DIR/info/sparse-checkout` as-is, so the contents of that file at this point would be ---------------- /* !unwanted ---------------- See also the "Sparse Checkout" section of linkgit:git-read-tree[1] to learn more about the gitignore-style patterns used in sparse checkouts. INTERNALS -- CONE PATTERN SET ----------------------------- In cone mode, only directories are accepted, but they are translated into the same gitignore-style patterns used in the full pattern set. We refer to the particular patterns used in those mode as being of one of two types: 1. *Recursive:* All paths inside a directory are included. 2. *Parent:* All files immediately inside a directory are included. Since cone mode always includes files at the toplevel, when running `git sparse-checkout set` with no directories specified, the toplevel directory is added as a parent pattern. At this point, the sparse-checkout file contains the following patterns: ---------------- /* !/*/ ---------------- This says "include everything immediately under the toplevel directory, but nothing at any level below that." When in cone mode, the `git sparse-checkout set` subcommand takes a list of directories. The command `git sparse-checkout

When changing sparse-checkout patterns in cone mode, Git checks for untracked files in excluded directories and warns if they exist. The full pattern set allows for complex inclusion/exclusion rules, but can be slow, whereas cone mode uses a restricted pattern set for better performance. The sparse-checkout file uses gitignore-style patterns to select included files, and in cone mode, directories are translated into these patterns to include recursive or parent directories.