source/docker.py: Document os/architecture as since 2.0.1
Technically these could not be used in 2.0.0 because validation would
reject these keys, so document this coherently.
diff --git a/src/buildstream_plugins/sources/docker.py b/src/buildstream_plugins/sources/docker.py
index 32768ef..45628fa 100644
--- a/src/buildstream_plugins/sources/docker.py
+++ b/src/buildstream_plugins/sources/docker.py
@@ -47,8 +47,11 @@
# will choose which image to use based on these settings. Default values
# are chosen based on the output of `uname -m` and `uname -s`, but you
# can override them.
- #architecture: arm64
- #os: linux
+ #
+ # architecture: arm64
+ # os: linux
+ #
+ # **Since**: 2.0.1
Note that Docker images may contain device nodes. BuildStream elements cannot
contain device nodes so those will be dropped. Any regular files in the /dev