GetLevelZeroHeaders: clone if absent, pull if exists

build_backend: do not delete level-zero git checkout in build_cmake if
present. Cmake is able to update existing checkout

Author: oleksandr-pavlyk

dpctl-capi/cmake/modules/GetLevelZeroHeaders.cmake

@@ -26,19 +26,37 @@
 
 function(get_level_zero_headers)
 
-    # Clone the Level Zero git repo
-    execute_process(
-        COMMAND ${GIT_EXECUTABLE} clone https://github.com/oneapi-src/level-zero.git
-        RESULT_VARIABLE result
-        ERROR_VARIABLE error
-        OUTPUT_STRIP_TRAILING_WHITESPACE
-        ERROR_STRIP_TRAILING_WHITESPACE
-    )
+    if(EXISTS level-zero)
+      # Update the checkout
+        execute_process(
+            COMMAND ${GIT_EXECUTABLE} fetch
+            RESULT_VARIABLE result
+            ERROR_VARIABLE error
+            WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/level-zero
+            OUTPUT_STRIP_TRAILING_WHITESPACE
+            ERROR_STRIP_TRAILING_WHITESPACE
+        )
 
-    if(NOT result EQUAL 0)
-        message(FATAL_ERROR
-            "Could not clone the Level Zero sources."
+        if(NOT result EQUAL 0)
+            message(FATAL_ERROR
+                "Could not update Level Zero sources."
+            )
+        endif()
+    else()
+        # Clone the Level Zero git repo
+        execute_process(
+            COMMAND ${GIT_EXECUTABLE} clone https://github.com/oneapi-src/level-zero.git
+            RESULT_VARIABLE result
+            ERROR_VARIABLE error
+            OUTPUT_STRIP_TRAILING_WHITESPACE
+            ERROR_STRIP_TRAILING_WHITESPACE
         )
+
+        if(NOT result EQUAL 0)
+            message(FATAL_ERROR
+                "Could not clone Level Zero sources from github.com/oneapi-src/level-zero."
+            )
+        endif()
     endif()
 
     # Use git describe to get latest tag name

scripts/build_backend.py

@@ -45,8 +45,20 @@
 dpctl_dir = os.getcwd()
 build_cmake_dir = os.path.join(dpctl_dir, "build_cmake")
 if os.path.exists(build_cmake_dir):
-    shutil.rmtree(build_cmake_dir)
-os.mkdir(build_cmake_dir)
+    for f in os.listdir(build_cmake_dir):
+        f_path = os.path.join(build_cmake_dir, f)
+        if os.path.isdir(f_path):
+            if (f == "level-zero") and os.path.isdir(
+                os.path.join(f_path, ".git")
+            ):
+                # do not delete Git checkout of level zero headers
+                pass
+            else:
+                shutil.rmtree(f_path)
+        else:
+            os.remove(f_path)
+else:
+    os.mkdir(build_cmake_dir)
 os.chdir(build_cmake_dir)
 
 INSTALL_PREFIX = os.path.join(dpctl_dir, "install")