merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/builtin/diff-index.c

@@ -0,0 +1,62 @@
+#define USE_THE_INDEX_COMPATIBILITY_MACROS
+#include "cache.h"
+#include "config.h"
+#include "diff.h"
+#include "commit.h"
+#include "revision.h"
+#include "builtin.h"
+#include "submodule.h"
+
+static const char diff_cache_usage[] =
+"git diff-index [-m] [--cached] "
+"[<common-diff-options>] <tree-ish> [<path>...]"
+COMMON_DIFF_OPTIONS_HELP;
+
+int cmd_diff_index(int argc, const char **argv, const char *prefix)
+{
+	struct rev_info rev;
+	int cached = 0;
+	int i;
+	int result;
+
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage(diff_cache_usage);
+
+	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
+	repo_init_revisions(the_repository, &rev, prefix);
+	rev.abbrev = 0;
+	precompose_argv(argc, argv);
+
+	argc = setup_revisions(argc, argv, &rev, NULL);
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+
+		if (!strcmp(arg, "--cached"))
+			cached = 1;
+		else
+			usage(diff_cache_usage);
+	}
+	if (!rev.diffopt.output_format)
+		rev.diffopt.output_format = DIFF_FORMAT_RAW;
+
+	/*
+	 * Make sure there is one revision (i.e. pending object),
+	 * and there is no revision filtering parameters.
+	 */
+	if (rev.pending.nr != 1 ||
+	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
+		usage(diff_cache_usage);
+	if (!cached) {
+		setup_work_tree();
+		if (read_cache_preload(&rev.diffopt.pathspec) < 0) {
+			perror("read_cache_preload");
+			return -1;
+		}
+	} else if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
+	result = run_diff_index(&rev, cached);
+	UNLEAK(rev);
+	return diff_result_code(&rev.diffopt, result);
+}