App code signing support

[taozuhong]

all apps distributed outside the App Store must be signed by the developer using an Apple-issued Developer ID certificate (combined with a private key) and notarized by Apple to run under the default Gatekeeper settings.

[freakboy3742]

Thanks for the suggestion. While signing is required, I think signing is out of scope for dmgbuild as a library.

dmgbuild is an API wrapper around the capabilities of hdiutil, and hdiutil doesn't have any native signing capabilities. Yes, the DMG needs to be signed; but so does the contents of the DMG; and the process of managing that signing requires a much more complex set of information and configuration.

I say this as someone who has implemented a wrapper for the signing process; Briefcase uses dmgbuild, and also performs signing - but the two concerns are quite separate.

There may be scope to extract some of the signing code from Briefcase into a standalone package; but that wouldn't involve adding the code into dmgbuild.

[taozuhong]

@freakboy3742 AppDMG / Create-DMG all support code signing, we should consider support it. appdmg

- code-sign (object, optional) - Options for codesigning the DMG
  - signing-identity (string, required) - The identity with which to sign the resulting DMG
  - identifier (string, optional) - Explicitly set the unique identifier string that is embedded in code signatures

Create-DMG --codesign <signature>: codesign the disk image with the specified signature

[freakboy3742]

Excellent. Good for them. That doesn't change the fact that I consider signing to be out-of-scope for dmgbuild.

If you're unhappy with the scope of dmgbuild, you're free to use a different package.