Fixes Homebrew/homebrew#30668

 - remove support for IO objects, since we no longer access ::DATA
   directly
 - since we don't need to support IO objects, use a separate class for
   string patches and stop wrapping strings in StringIO ojects

If both a formula and its dependencies are changed in a single pull
request it'll fail because the bottle block may no longer be correct.

Handle this case by ignoring bottle pour failures and fetching the
source packages instead of bottles.

images

Closes Homebrew/homebrew#31120

Fixes Homebrew/homebrew#31052.

Right now this code only produces false positives. When we have real
support for renames, we can implement it more carefully.

Closes Homebrew/homebrew#31126.

This fix means that brew-test-bot can bottle formulae that require GCC
again.

Without this it’s impossible for brew-test-bot to be able to verify if
installing GCC has allowed it to fix a compiler selection failure.

Closes Homebrew/homebrew#31025.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Per the `git-rev-parse(1)` manpage:

  --verify Verify that exactly one parameter is provided, and that it
  can be turned into a raw 20-byte SHA-1 that can be used to access the
  object database. If so, emit it to the standard output; otherwise,
  error out.

  If you want to make sure that the output actually names an object in
  your object database and/or can be used as a specific type of object
  For example, git rev-parse "$VAR^{commit}" will make sure $VAR names
  an existing object that is a commit-ish (i.e. a commit, or an
  annotated tag that points at a commit).

That actually means that:

  git rev-parse --verify af8e768e2bd3b4398bca033998f83b0eb8874914

will _always_ return the SHA-1 hash — regardless of whether or not
that's actually a valid reference!

Thus, when `GitDownloadStragtegy#update_repo` tries to check
`has_ref?`, it mistakenly succeeds, and doesn't actually do a `git fetch
origin`.

The fix is to use:

  git rev-parse --verify "af8e768e2bd3b4398bca033998f83b0eb8874914^{commit}"

Fixes Homebrew/homebrew#31045.
Closes Homebrew/homebrew#31054.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>