Fix #996 Remove any need for python during build

We are now using only CMake to generate `GitRef.hpp`. This should make it easier to build on Windows.
We use git's pretty formatting instead of rev-parse to output the full file in a single command, then CMake's `copy_if_different` to avoid unnecessary rebuilds.

Trick is to use %n for newlines and %x22 for quotes. See https://git-scm.com/docs/pretty-formats

We also output "unknown" and a warning when git is not available.

extra/git-ref.py

@@ -1,30 +0,0 @@
-#!/bin/env python3
-
-import filecmp
-import subprocess
-import sys
-import os
-
-out = "GitRef.hpp"
-tmp = f"{out}.tmp"
-
-if len(sys.argv) > 1:
-    rev = sys.argv[1]
-else:
-    rev = "HEAD"
-
-try:
-    ref = subprocess.run(["git", "rev-parse", "--short", rev], check=True, capture_output=True).stdout.decode().strip()
-except subprocess.CalledProcessError:
-    ref = "unknown"
-
-if not os.path.exists(out):
-    with open(out, "w") as f:
-        print(f"#pragma once\n\nnamespace tracy {{ static inline const char* GitRef = \"{ref}\"; }}", file=f)
-else:
-    with open(tmp, "w") as f:
-        print(f"#pragma once\n\nnamespace tracy {{ static inline const char* GitRef = \"{ref}\"; }}", file=f)
-    if not filecmp.cmp(out, tmp, shallow=False):
-        os.replace(tmp, out)
-    else:
-        os.unlink(tmp)

profiler/CMakeLists.txt

@@ -189,12 +189,25 @@ if(NOT DEFINED GIT_REV)
     set(GIT_REV "HEAD")
 endif()
 
-find_package(Python3 COMPONENTS Interpreter REQUIRED)
-add_custom_target(git-ref
-    COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_LIST_DIR}/../extra/git-ref.py ${GIT_REV}
-    BYPRODUCTS GitRef.hpp
-)
-add_dependencies(${PROJECT_NAME} git-ref)
+find_package(Git)
+if(Git_FOUND)
+    add_custom_target(git-ref
+        COMMAND ${GIT_EXECUTABLE} log -1 "--format=#pragma once %nnamespace tracy { static inline const char* GitRef = %x22%h%x22; }" ${GIT_REV} > GitRef.hpp.tmp
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different GitRef.hpp.tmp GitRef.hpp
+        BYPRODUCTS GitRef.hpp GitRef.hpp.tmp
+        VERBATIM
+    )
+    add_dependencies(${PROJECT_NAME} git-ref)
+else()
+    message(WARNING "git not found, using 'unknown' as git ref.")
+    add_custom_command(
+        OUTPUT GitRef.hpp
+        COMMAND ${CMAKE_COMMAND} -E echo "#pragma once" > GitRef.hpp
+        COMMAND ${CMAKE_COMMAND} -E echo "namespace tracy { static inline const char* GitRef = \"unknown\"; }" >> GitRef.hpp
+        VERBATIM
+    )
+    target_sources(${PROJECT_NAME} PUBLIC GitRef.hpp)
+endif()
 
 if(NOT EMSCRIPTEN)
     if(NOT NO_FILESELECTOR)