Four flag descriptions in --help are wrong (copy-paste errors)

[korya]

Problem

Current --help output:

      --assert-body string             Assert body equals the provided value
      --assert-header stringArray      Assert header equals the provided regexp
      --assert-header-eq stringArray   Assert header equals the provided regexp
      --assert-redirect string         Assert response redirects to the provided URL
      --assert-redirect-eq string      Assert response redirects to the provided URL

Flag	Says	Should say
--assert-body	"body equals the provided value"	matches the provided regexp
--assert-header	"header equals the provided regexp"	matches the provided regexp
--assert-header-eq	"header equals the provided regexp"	equals the provided value
--assert-redirect / --assert-redirect-eq	identical strings	one is a regexp, one is exact

Why it matters

--help is the only reference a user has at the terminal, and right now it cannot be used to tell the regexp variants from the exact-match ones — which is the single most important distinction in the whole flag set.

Affected code

main.go — registerAssertionFlags

Also worth documenting there

--assert-header-eq NAME with no value silently degrades to an "is present" assertion (parseHeaderAssertions), so there is no way to assert that a header equals the empty string.