Merge branch 'sl/diff-files-sparse' into seen

Teach "diff-files" not to expand sparse-index unless needed.

* sl/diff-files-sparse:
  diff-files: integrate with sparse index
  t1092: add tests for `git diff-files`

Author: gitster

builtin/diff-files.c

@@ -27,6 +27,10 @@ int cmd_diff_files(int argc, const char **argv, const char *prefix)
 		usage(diff_files_usage);
 
 	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
+
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	repo_init_revisions(the_repository, &rev, prefix);
 	rev.abbrev = 0;
 

t/perf/p2000-sparse-operations.sh

@@ -125,5 +125,7 @@ test_perf_on_all git checkout-index -f --all
 test_perf_on_all git update-index --add --remove $SPARSE_CONE/a
 test_perf_on_all "git rm -f $SPARSE_CONE/a && git checkout HEAD -- $SPARSE_CONE/a"
 test_perf_on_all git grep --cached --sparse bogus -- "f2/f1/f1/*"
+test_perf_on_all git diff-files
+test_perf_on_all git diff-files $SPARSE_CONE/a
 
 test_done

t/t1092-sparse-checkout-compatibility.sh

@@ -2055,4 +2055,65 @@ test_expect_success 'grep sparse directory within submodules' '
 	test_cmp actual expect
 '
 
+test_expect_success 'diff-files with pathspec inside sparse definition' '
+	init_repos &&
+
+	write_script edit-contents <<-\EOF &&
+	echo text >>"$1"
+	EOF
+
+	run_on_all ../edit-contents deep/a &&
+
+	test_all_match git diff-files &&
+
+	test_all_match git diff-files deep/a
+
+'
+
+test_expect_success 'diff-files with pathspec outside sparse definition' '
+	init_repos &&
+
+	write_script edit-contents <<-\EOF &&
+	echo text >>"$1"
+	EOF
+
+	# add file to the index but outside of cone
+	run_on_sparse mkdir newdirectory &&
+	run_on_sparse ../edit-contents newdirectory/testfile &&
+	test_sparse_match git add --sparse newdirectory/testfile &&
+
+	# file present on-disk without modifications
+	test_sparse_match git diff-files &&
+	test_must_be_empty sparse-checkout-out &&
+	test_must_be_empty sparse-checkout-err &&
+	test_sparse_match git diff-files newdirectory/testfile &&
+	test_must_be_empty sparse-checkout-out &&
+	test_must_be_empty sparse-checkout-err &&
+
+	# file present on-disk with modifications
+	FN=newdirectory/testfile &&
+	OID=$(git -C sparse-checkout hash-object $FN) &&
+	ZERO=$(test_oid zero) &&
+	echo ":100644 100644 $OID $ZERO M	$FN" >expect &&
+
+	run_on_sparse ../edit-contents newdirectory/testfile &&
+	test_sparse_match git diff-files &&
+	test_cmp expect sparse-checkout-out &&
+	test_sparse_match git diff-files newdirectory/testfile &&
+	test_cmp expect sparse-checkout-out
+'
+
+test_expect_success 'sparse index is not expanded: diff-files' '
+	init_repos &&
+
+	write_script edit-contents <<-\EOF &&
+	echo text >>"$1"
+	EOF
+
+	run_on_all ../edit-contents deep/a &&
+
+	ensure_not_expanded diff-files &&
+	ensure_not_expanded diff-files deep/a
+'
+
 test_done