allow passing user and branch to downstream

ci-support.sh

@@ -698,6 +698,8 @@ function install_ispc()
 function prepare_downstream_build()
 {
   local proj_name="$1"
+  local user_name="$2"
+  local branch_name="$3"
 
   # This is here because PyOpenCL needs to record a config change so
   # CL headers are found. It git adds siteconf.py.
@@ -707,10 +709,17 @@ function prepare_downstream_build()
     git commit -a -m "Fake commit to record local changes"
   fi
 
+  url="https://github.com/$user_name/$proj_name.git"
   if [[ "$proj_name" = "mirgecom" ]]; then
-      git clone "https://github.com/illinois-ceesd/$proj_name.git"
+    default_url="https://github.com/illinois-ceesd/$proj_name.git"
   else
-      git clone "https://github.com/inducer/$proj_name.git"
+    default_url="https://github.com/inducer/$proj_name.git"
+  fi
+
+  git clone "$url" --branch "$branch_name"
+  if [[ $? -ne 0 ]]; then
+    echo "*** Failed to clone '$url' branch '$branch_name'. Reverting to default."
+    git clone "$default_url"
   fi
 
   cd "$proj_name"
@@ -748,6 +757,8 @@ function prepare_downstream_build()
 function test_downstream()
 {
   local downstream_proj="$1"
+  local downstream_user="${2:-inducer}"
+  local downstream_branch="${3:-main}"
   local proj_name="$downstream_proj"
   local test_examples=0
 
@@ -756,7 +767,7 @@ function test_downstream()
     test_examples=1
   fi
 
-  prepare_downstream_build "$proj_name"
+  prepare_downstream_build "$proj_name" "$downstream_user" "$downstream_branch"
   build_py_project_in_conda_env
 
   if [[ "$test_examples" == "0" ]]; then