feat: add inherit to override (#1730)

* feat: add inherit to override

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* refactor: use dict and support prepend

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Refactor: simplifying by splitting the responsibilities of _dig_first

* Refactor to allow merging of string settings, and preserve table cascades

* docs: add some docs for inherit

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Apply suggestions from code review

Co-authored-by: Joe Rickerby <joerick@mac.com>

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Joe Rickerby <joerick@mac.com>

cibuildwheel/resources/cibuildwheel.schema.json

@@ -4,6 +4,17 @@
   "additionalProperties": false,
   "description": "cibuildwheel's settings.",
   "type": "object",
+  "defines": {
+    "inherit": {
+      "enum": [
+        "none",
+        "prepend",
+        "append"
+      ],
+      "default": "none",
+      "description": "How to inherit the parent's value."
+    }
+  },
   "properties": {
     "archs": {
       "description": "Change the architectures built on your machine by default.",
@@ -423,6 +434,45 @@
               }
             ]
           },
+          "inherit": {
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+              "before-all": {
+                "$ref": "#/defines/inherit"
+              },
+              "before-build": {
+                "$ref": "#/defines/inherit"
+              },
+              "before-test": {
+                "$ref": "#/defines/inherit"
+              },
+              "config-settings": {
+                "$ref": "#/defines/inherit"
+              },
+              "container-engine": {
+                "$ref": "#/defines/inherit"
+              },
+              "environment": {
+                "$ref": "#/defines/inherit"
+              },
+              "environment-pass": {
+                "$ref": "#/defines/inherit"
+              },
+              "repair-wheel-command": {
+                "$ref": "#/defines/inherit"
+              },
+              "test-command": {
+                "$ref": "#/defines/inherit"
+              },
+              "test-extras": {
+                "$ref": "#/defines/inherit"
+              },
+              "test-requires": {
+                "$ref": "#/defines/inherit"
+              }
+            }
+          },
           "before-all": {
             "$ref": "#/properties/before-all"
           },