ENT-11346: Added the 'cfbs render-input' command

[larsewi]

Converts input data for a module into an augments file (def.json). It does the same conversion as the input build step performs during cfbs build, except that the input data is read from an infile and nothing is stored in the built project.

Mission Portal needs this to render the augment for module input which is entered per host group, and thus stored in its database rather than in the project.

$ cfbs init
 ---snip---
$ cfbs get-input uninstall-packages - | jq '.[0].response += [{"name": "curl", "why": "its cool"}]' | cfbs render-input uninstall-packages - -
{
  "variables": {
    "uninstall_packages:uninstall_packages.package_names": {
      "value": [{ "name": "curl", "why": "its cool" }],
      "comment": "Added by 'cfbs input'"
    }
  }
}

The first 3 commits are preparatory refactoring, with no functional change. The next 3 fix pre-existing crashes found while implementing this, each with a shell test which fails without its fix.

Ticket: ENT-11346

🤖 Generated with Claude Code

[olehermanse]

Looks a bit unnecessarily complicated IMO, don't know exactly what's the best way.

Something like this feels more natural for me;

Suggested change

	# ExitStack rather than a plain with statement, so that the OSError
	# handling only covers opening the file, not running the command:
	with contextlib.ExitStack() as stack:
	# Open the infile first, so that a mistyped infile doesn't truncate
	# the outfile:
	try:
	infile = stack.enter_context(open_file_arg(infilename, "r"))
	except OSError as e:
	log.error("Can't open '%s': %s" % (infilename, e))
	return 1
	try:
	outfile = stack.enter_context(open_file_arg(outfilename, "w"))
	except OSError as e:
	log.error("Can't open '%s': %s" % (outfilename, e))
	return 1
	return commands.render_input_command(module, infile, outfile)
	unexpected = None
	try:
	with open(inp, "r") as infile:
	with open(out, "w") as outfile:
	try:
	commands.render_input_command(module, infile, outfile)
	except Exception as e:
	unexpected = e
	except OSError as e:
	log.error("Can't open '%s': %s" % (outfilename, e))
	return 1
	if unexpected:
	raise unexpected

[larsewi]

Yeah, I think both versions looks complicated