sparse-checkout: create 'init' subcommand

Getting started with a sparse-checkout file can be daunting. Help
users start their sparse enlistment using 'git sparse-checkout init'.
This will set 'core.sparseCheckout=true' in their config, write
an initial set of patterns to the sparse-checkout file, and update
their working directory.

Make sure to use the `extensions.worktreeConfig` setting and write
the sparse checkout config to the worktree-specific config file.
This avoids confusing interactions with other worktrees.

The use of running another process for 'git read-tree' is sub-
optimal. This will be removed in a later change.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/Documentation/git-sparse-checkout.txt b/Documentation/git-sparse-checkout.txt
index 87ffcbbcb0..491be1345f 100644
--- a/Documentation/git-sparse-checkout.txt
+++ b/Documentation/git-sparse-checkout.txt
@@ -30,6 +30,17 @@ COMMANDS
 'list'::
 	Provide a list of the contents in the sparse-checkout file.
 
+'init'::
+	Enable the `core.sparseCheckout` setting. If the
+	sparse-checkout file does not exist, then populate it with
+	patterns that match every file in the root directory and
+	no other directories, then will remove all directories tracked
+	by Git. Add patterns to the sparse-checkout file to
+	repopulate the working directory.
++
+To avoid interfering with other worktrees, it first enables the
+`extensions.worktreeConfig` setting and makes sure to set the
+`core.sparseCheckout` setting in the worktree-specific config file.
 
 SPARSE CHECKOUT
 ---------------