t/helper: improve "genrandom" test helper

The `test-tool genrandom` test helper can be used to generate random
data, either as an infinite stream or with a specified number of bytes.
The way we handle parsing the number of bytes is lacking though:

  - We don't have good error handling, so if the caller for example uses
    `test-tool genrandom 200xyz` then we'll end up generating 200 bytes
    of random data successfully.

  - Many callers want to generate e.g. 1 kilobyte or megabyte of data,
    but they have to either use unwieldy numbers like 1048576, or they
    have to precompute them.

Fix both of these issues by using `git_parse_ulong()` to parse the
argument. This function has better error handling, and it knows to
handle unit suffixes.

Adapt a couple of our tests to use suffixes instead of manual
computations.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-genrandom.c

@@ -6,6 +6,7 @@
 
 #include "test-tool.h"
 #include "git-compat-util.h"
+#include "parse.h"
 
 int cmd__genrandom(int argc, const char **argv)
 {
@@ -22,7 +23,9 @@ int cmd__genrandom(int argc, const char **argv)
 		next = next * 11 + *c;
 	} while (*c++);
 
-	count = (argc == 3) ? strtoul(argv[2], NULL, 0) : ULONG_MAX;
+	count = ULONG_MAX;
+	if (argc == 3 && !git_parse_ulong(argv[2], &count))
+		return error_errno("cannot parse argument '%s'", argv[2]);
 
 	while (count--) {
 		next = next * 1103515245 + 12345;

t/t1006-cat-file.sh

@@ -643,7 +643,7 @@ test_expect_success 'object reference via commit text search' '
 '
 
 test_expect_success 'setup blobs which are likely to delta' '
-	test-tool genrandom foo 10240 >foo &&
+	test-tool genrandom foo 10k >foo &&
 	{ cat foo && echo plus; } >foo-plus &&
 	git add foo foo-plus &&
 	git commit -m foo &&

t/t1050-large.sh

@@ -104,9 +104,9 @@ test_expect_success 'packsize limit' '
 		# mid1 and mid2 will fit within 256k limit but
 		# appending mid3 will bust the limit and will
 		# result in a separate packfile.
-		test-tool genrandom "a" $(( 66 * 1024 )) >mid1 &&
-		test-tool genrandom "b" $(( 80 * 1024 )) >mid2 &&
-		test-tool genrandom "c" $(( 128 * 1024 )) >mid3 &&
+		test-tool genrandom "a" 66k >mid1 &&
+		test-tool genrandom "b" 80k >mid2 &&
+		test-tool genrandom "c" 128k >mid3 &&
 		git add mid1 mid2 mid3 &&
 
 		count=0 &&

t/t1450-fsck.sh

@@ -918,7 +918,7 @@ test_expect_success 'fsck detects trailing loose garbage (large blob)' '
 test_expect_success 'fsck detects truncated loose object' '
 	# make it big enough that we know we will truncate in the data
 	# portion, not the header
-	test-tool genrandom truncate 4096 >file &&
+	test-tool genrandom truncate 4k >file &&
 	blob=$(git hash-object -w file) &&
 	file=$(sha1_file $blob) &&
 	test_when_finished "remove_object $blob" &&

t/t5301-sliding-window.sh

@@ -12,7 +12,7 @@ test_expect_success 'setup' '
 	for i in a b c
 	do
 	echo $i >$i &&
-	test-tool genrandom "$i" 32768 >>$i &&
+	test-tool genrandom "$i" 32k >>$i &&
 	git update-index --add $i || return 1
 	done &&
 	echo d >d && cat c >>d && git update-index --add d &&

t/t5310-pack-bitmaps.sh

@@ -242,7 +242,7 @@ test_bitmap_cases () {
 	'
 
 	test_expect_success 'splitting packs does not generate bogus bitmaps' '
-		test-tool genrandom foo $((1024 * 1024)) >rand &&
+		test-tool genrandom foo 1m >rand &&
 		git add rand &&
 		git commit -m "commit with big file" &&
 		git -c pack.packSizeLimit=500k repack -adb &&

t/t5710-promisor-remote-capability.sh

@@ -20,7 +20,7 @@ test_expect_success 'setup: create "template" repository' '
 	test_commit -C template 1 &&
 	test_commit -C template 2 &&
 	test_commit -C template 3 &&
-	test-tool genrandom foo 10240 >template/foo &&
+	test-tool genrandom foo 10k >template/foo &&
 	git -C template add foo &&
 	git -C template commit -m foo
 '
@@ -376,7 +376,7 @@ test_expect_success "clone with promisor.advertise set to 'true' but don't delet
 
 test_expect_success "setup for subsequent fetches" '
 	# Generate new commit with large blob
-	test-tool genrandom bar 10240 >template/bar &&
+	test-tool genrandom bar 10k >template/bar &&
 	git -C template add bar &&
 	git -C template commit -m bar &&
 

t/t7700-repack.sh

@@ -319,7 +319,7 @@ test_expect_success 'no bitmaps created if .keep files present' '
 
 test_expect_success 'auto-bitmaps do not complain if unavailable' '
 	test_config -C bare.git pack.packSizeLimit 1M &&
-	blob=$(test-tool genrandom big $((1024*1024)) |
+	blob=$(test-tool genrandom big 1m |
 	       git -C bare.git hash-object -w --stdin) &&
 	git -C bare.git update-ref refs/tags/big $blob &&
 
@@ -495,9 +495,9 @@ test_expect_success '--filter works with --max-pack-size' '
 		cd max-pack-size &&
 		test_commit base &&
 		# two blobs which exceed the maximum pack size
-		test-tool genrandom foo 1048576 >foo &&
+		test-tool genrandom foo 1m >foo &&
 		git hash-object -w foo &&
-		test-tool genrandom bar 1048576 >bar &&
+		test-tool genrandom bar 1m >bar &&
 		git hash-object -w bar &&
 		git add foo bar &&
 		git commit -m "adding foo and bar"