Add CacheKey config to override cache_tree_paths

mkosi/__init__.py

@@ -1776,6 +1776,7 @@ def finalize_default_initrd(
         *(["--output-dir", str(output_dir)] if output_dir else []),
         *(["--workspace-dir", str(config.workspace_dir)] if config.workspace_dir else []),
         *(["--cache-dir", str(config.cache_dir)] if config.cache_dir else []),
+        *(["--cache-key", config.cache_key]),
         *(["--package-cache-dir", str(config.package_cache_dir)] if config.package_cache_dir else []),
         *(["--local-mirror", str(config.local_mirror)] if config.local_mirror else []),
         "--incremental", str(config.incremental),
@@ -2776,7 +2777,7 @@ def print_output_size(path: Path) -> None:
 
 
 def cache_tree_paths(config: Config) -> tuple[Path, Path, Path]:
-    fragments = [config.distribution, config.release, config.architecture]
+    fragments = [config.cache_key]
 
     if config.image:
         fragments += [config.image]

mkosi/config.py

@@ -1162,6 +1162,7 @@ class ConfigSetting:
     default: Any = None
     default_factory: Optional[ConfigDefaultCallback] = None
     default_factory_depends: tuple[str, ...] = tuple()
+    default_expand_specifiers: bool = False
     paths: tuple[str, ...] = ()
     path_read_text: bool = False
     path_secret: bool = False
@@ -1399,6 +1400,7 @@ class Config:
     output_dir: Optional[Path]
     workspace_dir: Optional[Path]
     cache_dir: Optional[Path]
+    cache_key: str
     package_cache_dir: Optional[Path]
     build_dir: Optional[Path]
     image_id: Optional[str]
@@ -2057,6 +2059,14 @@ def parse_ini(path: Path, only_sections: Collection[str] = ()) -> Iterator[tuple
         help="Incremental cache directory",
         universal=True,
     ),
+    ConfigSetting(
+        dest="cache_key",
+        section="Output",
+        default="%d~%r~%a",
+        default_expand_specifiers=True,
+        help="Key to use inside incremental cache directory",
+        universal=True,
+    ),
     ConfigSetting(
         dest="package_cache_dir",
         metavar="PATH",
@@ -3525,6 +3535,9 @@ def finalize_value(setting: ConfigSetting) -> Optional[Any]:
         else:
             default = setting.parse(None, None)
 
+        if setting.default_expand_specifiers:
+            default = expand_specifiers(default, ParseContext.cli.directory)
+
         setattr(ParseContext.config, setting.dest, default)
 
         return default
@@ -4046,6 +4059,7 @@ def bold(s: Any) -> str:
                    Output Directory: {config.output_dir_or_cwd()}
                 Workspace Directory: {config.workspace_dir_or_default()}
                     Cache Directory: {none_to_none(config.cache_dir)}
+                          Cache Key: {config.cache_key}
             Package Cache Directory: {none_to_default(config.package_cache_dir)}
                     Build Directory: {none_to_none(config.build_dir)}
                            Image ID: {config.image_id}

tests/test_json.py

@@ -109,6 +109,7 @@ def test_config() -> None:
             ],
             "BuildSourcesEphemeral": true,
             "CacheDirectory": "/is/this/the/cachedir",
+            "CacheKey": "my_cache_key",
             "CacheOnly": "always",
             "Checksum": false,
             "CleanPackageMetadata": "auto",
@@ -371,6 +372,7 @@ def test_config() -> None:
         build_sources=[ConfigTree(Path("/qux"), Path("/frob"))],
         build_sources_ephemeral=True,
         cache_dir=Path("/is/this/the/cachedir"),
+        cache_key="my_cache_key",
         cacheonly=Cacheonly.always,
         checksum= False,
         clean_package_metadata=ConfigFeature.auto,