add: implement the --sparse option

We previously modified 'git add' to refuse updating index entries
outside of the sparse-checkout cone. This is justified to prevent users
from accidentally getting into a confusing state when Git removes those
files from the working tree at some later point.

Unfortunately, this caused some workflows that were previously possible
to become impossible, especially around merge conflicts outside of the
sparse-checkout cone. These were documented in tests within t1092.

We now re-enable these workflows using a new '--sparse' option to 'git
add'. This allows users to signal "Yes, I do know what I'm doing with
these files," and accept the consequences of the files leaving the
worktree later.

We delay updating the advice message until implementing a similar option
in 'git rm' and 'git mv'.

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

1 files changed, 16 insertions, 1 deletions

diff --git a/t/t3705-add-sparse-checkout.sh b/t/t3705-add-sparse-checkout.sh
index be6809eed2..3cab82092d 100755
--- a/t/t3705-add-sparse-checkout.sh
+++ b/t/t3705-add-sparse-checkout.sh
@@ -167,7 +167,13 @@ test_expect_success 'git add fails outside of sparse-checkout definition' '
 
 	git update-index --no-skip-worktree sparse_entry &&
 	test_must_fail git add sparse_entry &&
-	test_sparse_entry_unstaged
+	test_sparse_entry_unstaged &&
+
+	# Avoid munging CRLFs to avoid an error message
+	git -c core.autocrlf=input add --sparse sparse_entry 2>stderr &&
+	test_must_be_empty stderr &&
+	test-tool read-cache --table >actual &&
+	grep "^100644 blob.*sparse_entry\$" actual
 '
 
 test_expect_success 'add obeys advice.updateSparsePath' '
@@ -178,4 +184,13 @@ test_expect_success 'add obeys advice.updateSparsePath' '
 
 '
 
+test_expect_success 'add allows sparse entries with --sparse' '
+	git sparse-checkout set a &&
+	echo modified >sparse_entry &&
+	test_must_fail git add sparse_entry &&
+	test_sparse_entry_unchanged &&
+	git add --sparse sparse_entry 2>stderr &&
+	test_must_be_empty stderr
+'
+
 test_done