Clarification about 'docker build --build-arg'
See
@@ -299,6 +299,9 @@ accessed like regular environment variables in the `RUN` instruction of the
Dockerfile. Also, these values don't persist in the intermediate or final images
like `ENV` values do.
+Using this flag will not alter the output you see when the `ARG` lines from the
+Dockerfile are echoed during the build process.
+
For detailed information on using `ARG` and `ENV` instructions, see the
[Dockerfile reference](../builder.md).
