Merge branch 'ag/t7004-modernize'

Coding style fixes to a test script.

* ag/t7004-modernize:
  t7004: make use of write_script
  t7004: use single quotes instead of double quotes
  t7004: begin the test body on the same line as test_expect_success
  t7004: description on the same line as test_expect_success
  t7004: do not prepare things outside test_expect_success
  t7004: use indented here-doc
  t7004: one command per line
  t7004: remove space after redirect operators