impl: add a warning and env variable in the git commit grabber

scripts/get_git_commit.py

@@ -1,14 +1,21 @@
 import subprocess
+import os
 
 revision = "00000000000000000000000000000000000000000"
 
+if os.environ["GIT_REV"] != "":
+    revision = os.environ["GIT_REV"]
+
 try:
     revision = (
         subprocess.check_output(["git", "rev-parse", "HEAD"])
         .strip()
         .decode("utf-8")
     )
-except:
-    pass
+except Exception:
+    print("==========================================================================")
+    print("  WARNING: You are not in a Git repository or do not have Git installed.")
+    print("           The version string will be incorrect.")
+    print("==========================================================================")
 
 print(f"'-DGIT_REV=\"{revision}\"'")