t5303: use printf to generate delta bases

The exact byte count of the delta base file is important.
The test-delta helper will feed it to patch_delta(), which
will barf if it doesn't match the size byte given in the
delta. Using "echo" may end up with unexpected line endings
on some platforms (e.g,. "\r\n" instead of just "\n").

This actually wouldn't cause the test to fail (since we
already expect test-delta to complain about these bogus
deltas), but would mean that we're not exercising the code
we think we are.

Let's use printf instead (which we already trust to give us
byte-perfect output when we generate the deltas).

While we're here, let's tighten the 5-byte result size used
in the "truncated copy parameters" test. This just needs to
have enough room to attempt to parse the bogus copy command,
meaning 2 is sufficient. Using 5 was arbitrary and just
copied from the base size; since those no longer match, it's
simply confusing. Let's use a more meaningful number.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5303-pack-corruption-resilience.sh

@@ -327,15 +327,15 @@ test_expect_success \
     'printf "\0\1\2XX" > too_big_literal &&
      test_must_fail test-tool delta -p /dev/null too_big_literal /dev/null'
 
-# \5 - five bytes in base
+# \4 - four bytes in base
 # \1 - one byte in result
 # \221 - copy, one byte offset, one byte size
 #   \0 - copy from offset 0
 #   \2 - copy two bytes (one too many)
 test_expect_success \
     'apply delta with too many copied bytes' \
-    'printf "\5\1\221\0\2" > too_big_copy &&
-     echo base >base &&
+    'printf "\4\1\221\0\2" > too_big_copy &&
+     printf base >base &&
      test_must_fail test-tool delta -p base too_big_copy /dev/null'
 
 # \0 - empty base
@@ -356,8 +356,8 @@ test_expect_success \
     'printf "\0\1\221\0\1" > truncated_base &&
      test_must_fail test-tool delta -p /dev/null truncated_base /dev/null'
 
-# \5 - five bytes in base
-# \5 - five bytes in result
+# \4 - four bytes in base
+# \2 - two bytes in result
 # \1 - one literal byte (X)
 # \221 - copy, one byte offset, one byte size
 #        (offset/size missing)
@@ -366,8 +366,8 @@ test_expect_success \
 # delta size check.
 test_expect_success \
     'apply delta with truncated copy parameters' \
-    'printf "\5\5\1X\221" > truncated_copy_delta &&
-     echo base >base &&
+    'printf "\4\2\1X\221" > truncated_copy_delta &&
+     printf base >base &&
      test_must_fail test-tool delta -p base truncated_copy_delta /dev/null'
 
 # \0 - empty base
@@ -379,7 +379,7 @@ test_expect_success \
     'printf "\0\1\1X\1" > tail_garbage_literal &&
      test_must_fail test-tool delta -p /dev/null tail_garbage_literal /dev/null'
 
-# \5 - five bytes in base
+# \4 - four bytes in base
 # \1 - one byte in result
 # \1 - one literal byte (X)
 # \221 - copy, one byte offset, one byte size
@@ -387,8 +387,8 @@ test_expect_success \
 #   \1 - copy 1 byte
 test_expect_success \
     'apply delta with trailing garbage copy' \
-    'printf "\5\1\1X\221\0\1" > tail_garbage_copy &&
-     echo base >base &&
+    'printf "\4\1\1X\221\0\1" > tail_garbage_copy &&
+     printf base >base &&
      test_must_fail test-tool delta -p /dev/null tail_garbage_copy /dev/null'
 
 # \0 - empty base