Document the ":module{.tag}" syntax in a more visible place.
Taken from the comment for OutputFileProducer in android/module.go.
Test: n/a
Change-Id: If74e9072333ed2acd51e1019d5e756cf54c9e55e
diff --git a/README.md b/README.md
index 73aa1ed..37feb1d 100644
--- a/README.md
+++ b/README.md
@@ -36,13 +36,28 @@
For a list of valid module types and their properties see
[$OUT_DIR/soong/docs/soong_build.html](https://ci.android.com/builds/latest/branches/aosp-build-tools/targets/linux/view/soong_build.html).
-### Globs
+### File lists
-Properties that take a list of files can also take glob patterns. Glob
-patterns can contain the normal Unix wildcard `*`, for example "*.java". Glob
-patterns can also contain a single `**` wildcard as a path element, which will
-match zero or more path elements. For example, `java/**/*.java` will match
-`java/Main.java` and `java/com/android/Main.java`.
+Properties that take a list of files can also take glob patterns and output path
+expansions.
+
+* Glob patterns can contain the normal Unix wildcard `*`, for example `"*.java"`.
+
+ Glob patterns can also contain a single `**` wildcard as a path element, which
+ will match zero or more path elements. For example, `java/**/*.java` will match
+ `java/Main.java` and `java/com/android/Main.java`.
+
+* Output path expansions take the format `:module` or `:module{.tag}`, where
+ `module` is the name of a module that produces output files, and it expands to
+ a list of those output files. With the optional `{.tag}` suffix, the module
+ may produce a different list of outputs according to `tag`.
+
+ For example, a `droiddoc` module with the name "my-docs" would return its
+ `.stubs.srcjar` output with `":my-docs"`, and its `.doc.zip` file with
+ `":my-docs{.doc.zip}"`.
+
+ This is commonly used to reference `filegroup` modules, whose output files
+ consist of their `srcs`.
### Variables
@@ -64,6 +79,7 @@
referenced.
### Comments
+
Android.bp files can contain C-style multiline `/* */` and C++ style single-line
`//` comments.