Prevent compiling the whole project on each commit.

Putting the git information into a generated sourcefile prevents
recompiling the whole project after each commit.

pio-scripts/auto_firmware_version.py

@@ -2,6 +2,7 @@
 #
 # Copyright (C) 2022 Thomas Basler and others
 #
+import os
 import pkg_resources
 
 Import("env")
@@ -15,15 +16,64 @@ if missing_pkgs:
 
 from dulwich import porcelain
 
-def get_firmware_specifier_build_flag():
+
+def updateFileIfChanged(filename, content):
+    mustUpdate = True
+    try:
+        fp = open(filename, "rb")
+        if fp.read() == content:
+            mustUpdate = False
+        fp.close()
+    except:
+        pass
+    if mustUpdate:
+        fp = open(filename, "wb")
+        fp.write(content)
+        fp.close()
+    return mustUpdate
+
+
+def get_build_version():
     try:
         build_version = porcelain.describe('.')  # '.' refers to the repository root dir
     except:
         build_version = "g0000000"
-    build_flag = "-D AUTO_GIT_HASH=\\\"" + build_version + "\\\""
     print ("Firmware Revision: " + build_version)
+    return build_version
+
+
+def get_firmware_specifier_build_flag():
+    build_version = get_build_version()
+    build_flag = "-D AUTO_GIT_HASH=\\\"" + build_version + "\\\""
     return (build_flag)
 
-env.Append(
-    BUILD_FLAGS=[get_firmware_specifier_build_flag()]
-)
+
+def do_main():
+    if 0:
+        # this results in a full recompilation of the whole project after each commit
+        env.Append(
+            BUILD_FLAGS=[get_firmware_specifier_build_flag()]
+        )
+    else:
+        # we just create a .c file containing the needed datas
+        targetfile = os.path.join(env.subst("$BUILD_DIR"), "__compiled_constants.c")
+        lines = ""
+        lines += "/* Generated file within build process - Do NOT edit */\n"
+
+        if 0:
+            # Add the current date and time as string in UTC timezone
+            from datetime import datetime, timezone
+            now = datetime.now(tz=timezone.utc)
+            COMPILED_DATE_TIME_UTC_STR = now.strftime("%Y/%m/%d %H:%M:%S")
+            lines += 'const char *__COMPILED_DATE_TIME_UTC_STR__ = "%s";\n' % (COMPILED_DATE_TIME_UTC_STR)
+
+        if 1:
+            # Add the description of the current git revision
+            lines += 'const char *__COMPILED_GIT_HASH__ = "%s";\n' % (get_build_version())
+
+        updateFileIfChanged(targetfile, bytes(lines, "utf-8"))
+
+        # Add the created file to the buildfiles - platformio knows how to handle *.c files
+        env.AppendUnique(PIOBUILDFILES=[targetfile])
+
+do_main()