Add pubkey support

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>

README.md

@@ -24,6 +24,7 @@ Parameters
 | packages    | *none*                                       | List of additional packages to install.
 | install-dir | C:\cygwin                                    | Installation directory
 | site        | http://mirrors.kernel.org/sourceware/cygwin/ | Mirror sites to install from, separated by whitespace
+| pubkeys     | *none*                                       | Absolute paths of extra public key files (RFC4880 format), separated by whitespace
 | check-sig   | true                                         | Whether to check the setup.ini signature
 | add-to-path | true                                         | Whether to add Cygwin's `/bin` directory to the system `PATH`
 

action.yml

@@ -19,6 +19,9 @@ inputs:
     description: Should the setup.ini file signature be checked?
     required: false
     default: true
+  pubkeys:
+    description: Absolute paths of extra public key files (RFC4880 format), separated by whitespace
+    required: false
   site:
     description: Download site URLs separated by whitespace
     required: false
@@ -76,6 +79,16 @@ runs:
           $args += '-X'
         }
 
+        if ( '${{ inputs.pubkeys }}' ) {
+          $pubkeys = '${{ inputs.pubkeys }}'
+          $pubkey_list = $pubkeys.Split('', [System.StringSplitOptions]::RemoveEmptyEntries)
+          $pubkey_list = $pubkey_list | % { $_.Trim() }
+          foreach ($pubkey in $pubkey_list) {
+            $args += '-K'
+            $args += $pubkey
+          }
+        }
+
         if ($platform -eq 'x86') {
           $args += '--allow-unsupported-windows'
         }