feat: add git source support (#334)

* try to add git source support

* improve GIT_SOURCE output name

* fix syntax

---------

Co-authored-by: Bartek Pacia <barpac02@gmail.com>

action.yaml

@@ -46,6 +46,10 @@ inputs:
     description: If true, get outputs but do not install Flutter
     required: false
     default: "false"
+  git-source:
+    description: Git clone source
+    required: false
+    default: "https://github.com/flutter/flutter.git"
 
 outputs:
   CHANNEL:
@@ -69,6 +73,9 @@ outputs:
   PUB-CACHE-PATH:
     value: "${{ steps.flutter-action.outputs.PUB-CACHE-PATH }}"
     description: Path to pub cache
+  GIT_SOURCE:
+    value: "${{ steps.flutter-action.outputs.GIT_SOURCE }}"
+    description: Git source of Flutter SDK repository to clone
 
 runs:
   using: composite
@@ -97,6 +104,7 @@ runs:
           -c '${{ inputs.cache-path }}' \
           -l '${{ inputs.pub-cache-key }}' \
           -d '${{ inputs.pub-cache-path }}' \
+          -g '${{ inputs.git-source }}' \
           ${{ inputs.channel }}
 
     - name: Cache Flutter