Add optional input is_external_pr

.github/workflows/conan-recipe-version.yml

@@ -12,6 +12,11 @@ on:
                 default: ""
                 type: string
 
+            is_external_pr:
+                required: false
+                default: false
+                type: boolean
+
         outputs:
             recipe_id_full:
                 description: "The full Conan recipe id: <name>/<version>@<user>/<channel>"
@@ -53,14 +58,14 @@ jobs:
         steps:
             -   name: Checkout repo
                 uses: actions/checkout@v3
-                if: ${{ ! contains(github.event, 'pull_request') }}
+                if: ${{ ! is_external_pr }}
                 with:
                     fetch-depth: 0
                     ref: ${{ github.head_ref }}
 
             -   name: Checkout repo PR
                 uses: actions/checkout@v3
-                if: ${{ contains(github.event, 'pull_request') }}
+                if: ${{ is_external_pr }}
                 with:
                     fetch-depth: 0
                     ref: ${{ github.event.pull_request.head.ref }}