worktree: copy sparse-checkout patterns and config on add

When adding a new worktree, it is reasonable to expect that we want to
use the current set of sparse-checkout settings for that new worktree.
This is particularly important for repositories where the worktree would
become too large to be useful. This is even more important when using
partial clone as well, since we want to avoid downloading the missing
blobs for files that should not be written to the new worktree.

The only way to create such a worktree without this intermediate step of
expanding the full worktree is to copy the sparse-checkout patterns and
config settings during 'git worktree add'. Each worktree has its own
sparse-checkout patterns, and the default behavior when the
sparse-checkout file is missing is to include all paths at HEAD. Thus,
we need to have patterns from somewhere, they might as well be the
current worktree's patterns. These are then modified independently in
the future.

In addition to the sparse-checkout file, copy the worktree config file
if worktree config is enabled and the file exists. This will copy over
any important settings to ensure the new worktree behaves the same as
the current one. The only exception we must continue to make is that
core.bare and core.worktree should become unset in the worktree's config
file.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 8 deletions

diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index be6ea4ffe3..8a757b43e6 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -146,9 +146,9 @@ test_expect_success 'interaction with clone --no-checkout (unborn index)' '
 '
 
 test_expect_success 'set enables config' '
-	git init empty-config &&
+	git init worktree-config &&
 	(
-		cd empty-config &&
+		cd worktree-config &&
 		test_commit test file &&
 		test_path_is_missing .git/config.worktree &&
 		git sparse-checkout set nothing &&
@@ -201,6 +201,21 @@ test_expect_success 'add to sparse-checkout' '
 	check_files repo "a folder1 folder2"
 '
 
+test_expect_success 'worktree: add copies sparse-checkout patterns' '
+	cat repo/.git/info/sparse-checkout >old &&
+	test_when_finished cp old repo/.git/info/sparse-checkout &&
+	test_when_finished git -C repo worktree remove ../worktree &&
+	git -C repo sparse-checkout set --no-cone "/*" &&
+	git -C repo worktree add --quiet ../worktree 2>err &&
+	test_must_be_empty err &&
+	new="$(git -C worktree rev-parse --git-path info/sparse-checkout)" &&
+	test_path_is_file "$new" &&
+	test_cmp repo/.git/info/sparse-checkout "$new" &&
+	git -C worktree sparse-checkout set --cone &&
+	test_cmp_config -C worktree true core.sparseCheckoutCone &&
+	test_must_fail git -C repo core.sparseCheckoutCone
+'
+
 test_expect_success 'cone mode: match patterns' '
 	git -C repo config --worktree core.sparseCheckoutCone true &&
 	rm -rf repo/a repo/folder1 repo/folder2 &&
@@ -520,13 +535,13 @@ test_expect_success 'interaction with submodules' '
 '
 
 test_expect_success 'different sparse-checkouts with worktrees' '
+	git -C repo sparse-checkout set --cone deep folder1 &&
 	git -C repo worktree add --detach ../worktree &&
-	check_files worktree "a deep folder1 folder2" &&
-	git -C worktree sparse-checkout init --cone &&
-	git -C repo sparse-checkout set folder1 &&
-	git -C worktree sparse-checkout set deep/deeper1 &&
-	check_files repo a folder1 &&
-	check_files worktree a deep
+	check_files worktree "a deep folder1" &&
+	git -C repo sparse-checkout set --cone folder1 &&
+	git -C worktree sparse-checkout set --cone deep/deeper1 &&
+	check_files repo "a folder1" &&
+	check_files worktree "a deep"
 '
 
 test_expect_success 'set using filename keeps file on-disk' '