update-index: integrate with sparse index

Enable usage of the sparse index with `update-index`. Most variations of
`update-index` work without explicitly expanding the index (due to the
implicit expansion performed when attempting to find an existing entry).
However, in order to prevent manually creating a sparse directory cache
entry (current behavior is to throw an error when presented with a directory
using `--cacheinfo`), the index is expanded before the the entry is added.


Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

builtin/update-index.c

@@ -426,6 +426,10 @@ static int add_cacheinfo(unsigned int mode, const struct object_id *oid,
 		ce->ce_flags |= CE_VALID;
 	option = allow_add ? ADD_CACHE_OK_TO_ADD : 0;
 	option |= allow_replace ? ADD_CACHE_OK_TO_REPLACE : 0;
+
+	/* TODO: ensure full index to maintain expected behavior */
+	ensure_full_index(&the_index);
+
 	if (add_cache_entry(ce, option))
 		return error("%s: cannot add to the index - missing --add option?",
 			     path);
@@ -1083,6 +1087,9 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config, NULL);
 
+	prepare_repo_settings(r);
+	the_repository->settings.command_requires_full_index = 0;
+
 	/* we will diagnose later if it turns out that we need to update it */
 	newfd = hold_locked_index(&lock_file, 0);
 	if (newfd < 0)

t/t1092-sparse-checkout-compatibility.sh

@@ -1018,6 +1018,18 @@ test_expect_success 'sparse index is not expanded: sparse-checkout' '
 	ensure_not_expanded sparse-checkout set
 '
 
+test_expect_success 'sparse index is not expanded: update-index' '
+	init_repos &&
+
+	echo "test" >sparse-index/README.md &&
+	echo "test2" >sparse-index/a &&
+	rm -f sparse-index/deep/a &&
+
+	ensure_not_expanded update-index --add README.md &&
+	ensure_not_expanded update-index a &&
+	ensure_not_expanded update-index --remove deep/a &&
+'
+
 # NEEDSWORK: a sparse-checkout behaves differently from a full checkout
 # in this scenario, but it shouldn't.
 test_expect_success 'reset mixed and checkout orphan' '