merge(3p/git): Merge git subtree at v2.29.2

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

third_party/git/t/helper/test-path-utils.c

@@ -185,6 +185,99 @@ static int cmp_by_st_size(const void *a, const void *b)
 	return x > y ? -1 : (x < y ? +1 : 0);
 }
 
+/*
+ * A very simple, reproducible pseudo-random generator. Copied from
+ * `test-genrandom.c`.
+ */
+static uint64_t my_random_value = 1234;
+
+static uint64_t my_random(void)
+{
+	my_random_value = my_random_value * 1103515245 + 12345;
+	return my_random_value;
+}
+
+/*
+ * A fast approximation of the square root, without requiring math.h.
+ *
+ * It uses Newton's method to approximate the solution of 0 = x^2 - value.
+ */
+static double my_sqrt(double value)
+{
+	const double epsilon = 1e-6;
+	double x = value;
+
+	if (value == 0)
+		return 0;
+
+	for (;;) {
+		double delta = (value / x - x) / 2;
+		if (delta < epsilon && delta > -epsilon)
+			return x + delta;
+		x += delta;
+	}
+}
+
+static int protect_ntfs_hfs_benchmark(int argc, const char **argv)
+{
+	size_t i, j, nr, min_len = 3, max_len = 20;
+	char **names;
+	int repetitions = 15, file_mode = 0100644;
+	uint64_t begin, end;
+	double m[3][2], v[3][2];
+	uint64_t cumul;
+	double cumul2;
+
+	if (argc > 1 && !strcmp(argv[1], "--with-symlink-mode")) {
+		file_mode = 0120000;
+		argc--;
+		argv++;
+	}
+
+	nr = argc > 1 ? strtoul(argv[1], NULL, 0) : 1000000;
+	ALLOC_ARRAY(names, nr);
+
+	if (argc > 2) {
+		min_len = strtoul(argv[2], NULL, 0);
+		if (argc > 3)
+			max_len = strtoul(argv[3], NULL, 0);
+		if (min_len > max_len)
+			die("min_len > max_len");
+	}
+
+	for (i = 0; i < nr; i++) {
+		size_t len = min_len + (my_random() % (max_len + 1 - min_len));
+
+		names[i] = xmallocz(len);
+		while (len > 0)
+			names[i][--len] = (char)(' ' + (my_random() % ('\x7f' - ' ')));
+	}
+
+	for (protect_ntfs = 0; protect_ntfs < 2; protect_ntfs++)
+		for (protect_hfs = 0; protect_hfs < 2; protect_hfs++) {
+			cumul = 0;
+			cumul2 = 0;
+			for (i = 0; i < repetitions; i++) {
+				begin = getnanotime();
+				for (j = 0; j < nr; j++)
+					verify_path(names[j], file_mode);
+				end = getnanotime();
+				printf("protect_ntfs = %d, protect_hfs = %d: %lfms\n", protect_ntfs, protect_hfs, (end-begin) / (double)1e6);
+				cumul += end - begin;
+				cumul2 += (end - begin) * (end - begin);
+			}
+			m[protect_ntfs][protect_hfs] = cumul / (double)repetitions;
+			v[protect_ntfs][protect_hfs] = my_sqrt(cumul2 / (double)repetitions - m[protect_ntfs][protect_hfs] * m[protect_ntfs][protect_hfs]);
+			printf("mean: %lfms, stddev: %lfms\n", m[protect_ntfs][protect_hfs] / (double)1e6, v[protect_ntfs][protect_hfs] / (double)1e6);
+		}
+
+	for (protect_ntfs = 0; protect_ntfs < 2; protect_ntfs++)
+		for (protect_hfs = 0; protect_hfs < 2; protect_hfs++)
+			printf("ntfs=%d/hfs=%d: %lf%% slower\n", protect_ntfs, protect_hfs, (m[protect_ntfs][protect_hfs] - m[0][0]) * 100 / m[0][0]);
+
+	return 0;
+}
+
 int cmd__path_utils(int argc, const char **argv)
 {
 	if (argc == 3 && !strcmp(argv[1], "normalize_path_copy")) {
@@ -197,11 +290,14 @@ int cmd__path_utils(int argc, const char **argv)
 	}
 
 	if (argc >= 2 && !strcmp(argv[1], "real_path")) {
+		struct strbuf realpath = STRBUF_INIT;
 		while (argc > 2) {
-			puts(real_path(argv[2]));
+			strbuf_realpath(&realpath, argv[2], 1);
+			puts(realpath.buf);
 			argc--;
 			argv++;
 		}
+		strbuf_release(&realpath);
 		return 0;
 	}
 
@@ -355,6 +451,26 @@ int cmd__path_utils(int argc, const char **argv)
 		return !!res;
 	}
 
+	if (argc > 1 && !strcmp(argv[1], "protect_ntfs_hfs"))
+		return !!protect_ntfs_hfs_benchmark(argc - 1, argv + 1);
+
+	if (argc > 1 && !strcmp(argv[1], "is_valid_path")) {
+		int res = 0, expect = 1, i;
+
+		for (i = 2; i < argc; i++)
+			if (!strcmp("--not", argv[i]))
+				expect = 0;
+			else if (expect != is_valid_path(argv[i]))
+				res = error("'%s' is%s a valid path",
+					    argv[i], expect ? " not" : "");
+			else
+				fprintf(stderr,
+					"'%s' is%s a valid path\n",
+					argv[i], expect ? "" : " not");
+
+		return !!res;
+	}
+
 	fprintf(stderr, "%s: unknown function name: %s\n", argv[0],
 		argv[1] ? argv[1] : "(there was none)");
 	return 1;