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, 56 insertions, 2 deletions

diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
index 37ad79470f..43139af08f 100755
--- a/t/t2400-worktree-add.sh
+++ b/t/t2400-worktree-add.sh
@@ -165,8 +165,62 @@ test_expect_success '"add" default branch of a bare repo' '
 	(
 		git clone --bare . bare2 &&
 		cd bare2 &&
-		git worktree add ../there3 main
-	)
+		git worktree add ../there3 main &&
+		cd ../there3 &&
+		# Simple check that a Git command does not
+		# immediately fail with the current setup
+		git status
+	) &&
+	cat >expect <<-EOF &&
+	init.t
+	EOF
+	ls there3 >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '"add" to bare repo with worktree config' '
+	(
+		git clone --bare . bare3 &&
+		cd bare3 &&
+		git config extensions.worktreeconfig true &&
+
+		# Add config values that are erroneous to have in
+		# a config.worktree file outside of the main
+		# working tree, to check that Git filters them out
+		# when copying config during "git worktree add".
+		git config --worktree core.bare true &&
+		git config --worktree core.worktree "$(pwd)" &&
+
+		# We want to check that bogus.key is copied
+		git config --worktree bogus.key value &&
+		git config --unset core.bare &&
+		git worktree add ../there4 main &&
+		cd ../there4 &&
+
+		# Simple check that a Git command does not
+		# immediately fail with the current setup
+		git status &&
+		git worktree add --detach ../there5 &&
+		cd ../there5 &&
+		git status
+	) &&
+
+	# the worktree has the arbitrary value copied.
+	test_cmp_config -C there4 value bogus.key &&
+	test_cmp_config -C there5 value bogus.key &&
+
+	# however, core.bare and core.worktree were removed.
+	test_must_fail git -C there4 config core.bare &&
+	test_must_fail git -C there4 config core.worktree &&
+
+	cat >expect <<-EOF &&
+	init.t
+	EOF
+
+	ls there4 >actual &&
+	test_cmp expect actual &&
+	ls there5 >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'checkout with grafts' '