Fix sparse-checkout commit (Azure#23474)

Co-authored-by: Wes Haggard <[email protected]>

Author: azure-sdk

eng/common/pipelines/templates/jobs/prepare-pipelines.yml

@@ -5,6 +5,9 @@ parameters:
   - name: RepositoryPath
     type: string
     default: 'sdk'
+  - name: RepositoryCommitish
+    type: string
+    default: $(Build.SourceVersion)
 
 jobs:
 - job:
@@ -36,6 +39,7 @@ jobs:
       parameters:
         Repositories:
           - Name: ${{ parameters.Repository }}
+            Commitish: ${{ parameters.RepositoryCommitish }}
             WorkingDirectory: $(System.DefaultWorkingDirectory)
         Paths:
           - 'sdk/**/*.yml'