docs: add docs about include-groups

Author: finswimmer

docs/managing-dependencies.md

@@ -80,6 +80,30 @@ Optional group dependencies will **still** be resolved alongside other dependenc
 special care should be taken to ensure they are compatible with each other.
 {{% /warning %}}
 
+### Including Dependencies from Other Groups
+
+You can include dependencies from one group in another group.
+This is useful when you want to aggregate dependencies from multiple groups into a single group.
+
+```toml
+[tool.poetry.group.test.dependencies]
+pytest = "^6.0.0"
+
+[tool.poetry.group.lint.dependencies]
+black = "^20.8b1"
+
+[tool.poetry.group.dev]
+include-groups = [
+    "test",
+    "lint"
+]
+
+[tool.poetry.group.dev.dependencies]
+tox = "*"
+```
+
+In this example, the `dev` group includes all dependencies from the `test` and `lint` groups.
+
 ### Adding a dependency to a group
 
 The [`add`]({{< relref "cli#add" >}}) command is the preferred way to add dependencies

poetry.lock

@@ -4,7 +4,7 @@ version = "2.0.1"
 description = "Python dependency management and packaging made easy."
 requires-python = ">=3.9,<4.0"
 dependencies = [
-    "poetry-core @ git+https://github.com/python-poetry/poetry-core.git",
+    "poetry-core @ git+https://github.com/finswimmer/core.git@nested-dependency-groups",
     "build (>=1.2.1,<2.0.0)",
     "cachecontrol[filecache] (>=0.14.0,<0.15.0)",
     "cleo (>=2.1.0,<3.0.0)",