Re: [PATCH 7/7] sparse-checkout: make --cone the default and deprecate --no-cone

> From: Elijah Newren <newren@gmail.com>
> 
> Make --cone mode the default, and deprecate --no-cone mode.  While we
> have no current plans to actually remove --no-cone mode, we think users
> would be better off not using it.  Update the documentation accordingly,
> including explaining why we think non-cone mode is problematic for
> users.

> While at it, since the new default just uses directories and removes the
> need to understand patterns, we can mark multiple sections in the manual
> as "INTERNALS" to reflect the fact that users do not need to wade
> through those sections to understand how to use the command any more.
> We can instead add a simple EXAMPLES section to the manual which
> distills the necessary bits from the more complex INTERNALS sections.

> -SPARSE CHECKOUT
> ----------------
> +EXAMPLES
> +--------
> +`git sparse-checkout set MY/DIR1 SUB/DIR2`::
> +
> +	Change to a sparse-checkout with all files (at any depth) under
> +	MY/DIR1/ and SUB/DIR2/ present in the working copy (plus all
> +	files immediately under MY/ and SUB/ and the toplevel

> +	are present in the working copy to this new selection.  Note
> +	that this command will also delete all ignored files in any
> +	directory that no longer has either tracked or
> +	non-ignored-untracked files present.
> +
> +`git sparse-checkout disable`::
> +
> +	Repopulate the working directory with all files, disabling sparse
> +	checkouts.
> +
> +`git sparse-checkout add SOME/DIR/ECTORY`::
> +
> +	Add all files under SOME/DIR/ECTORY/ (at any depth) to the
> +	sparse checkout, as well as all files immediately under
> +	SOME/DIR/ and immediately under SOME/.  Must already be in a
> +	sparse checkout before using this command.
> +
> +`git sparse-checkout reapply`::
> +
> +	It is possible for commands to update the working tree in a way
> +	that does not respect the selected sparsity directories, either
> +	because of special cases (such as hitting conflicts when
> +	merging/rebasing), or because some commands didn't fully support
> +	sparse checkouts (e.g. the old `recursive` merge backend had
> +	only limited support).  This command reapplies the existing
> +	sparse directory specifications to make the working directory
> +	match.
> +
> +INTERNALS -- SPARSE CHECKOUT
> +----------------------------

> +INTERNALS -- NON-CONE PROBLEMS
> +------------------------------
> +
> +The `$GIT_DIR/info/sparse-checkout` file populated by the `set` and
> +`add` subcommands is defined to be a bunch of patterns (one per line)
> +using the same syntax as `.gitignore` files.  In cone mode, these
> +patterns are restricted to matching directories (and users only ever
> +need supply or see directory names), while in non-cone mode any
> +gitignore-style pattern is permitted.  Using the full gitignore-style
> +patterns in non-cone mode has a number of shortcomings:

> +INTERNALS -- FULL PATTERN SET
> +-----------------------------
> +
> +As noted above, the sparse-checkout file uses the same syntax as
> +`.gitignore` files; see linkgit:gitignore[5] for details.  Here, though,
> +the patterns are being used to select which files to include rather than
> +which files to exclude.
> +
> +To complicate things a bit further, while
> +`$GIT_DIR/info/sparse-checkout` is usually used to specify what files
> +are included, you can also specify what files are _not_ included, using
> +negative patterns. For example, to select everything, and then to remove
> +the file `unwanted`:

> -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 full pattern set allows for arbitrary pattern matches and
> +complicated inclusion/exclusion rules. As noted above, this can result
> +in O(N*M) pattern matches when updating the index, where N is the number

>  If your repository contains one or more submodules, then submodules
>  are populated based on interactions with the `git submodule` command.
> diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
> index 6e0af166f80..aa2c66f15e3 100644
> --- a/builtin/sparse-checkout.c
> +++ b/builtin/sparse-checkout.c
> @@ -395,13 +395,13 @@ static int update_modes(int *cone_mode, int *sparse_index)
>  
>  	/* Set cone/non-cone mode appropriately */
>  	core_apply_sparse_checkout = 1;
> -	if (*cone_mode == 1) {
> +	if (*cone_mode == 1 || *cone_mode == -1) {
>  		mode = MODE_CONE_PATTERNS;
> -		core_sparse_checkout_cone = 1;
> +		if (record_mode)
> +			core_sparse_checkout_cone = 1;
>  	} else {
>  		mode = MODE_ALL_PATTERNS;
> -		if (record_mode)
> -			core_sparse_checkout_cone = 0;
> +		core_sparse_checkout_cone = 0;
>  	}