[OPENJDK-1963] document MAVEN_MIRRORS upcasing behaviour

rewrite description of MAVEN_MIRRORS to properly document the format
of the parameter (uppercase, dashes get replaced with underscores).

Signed-off-by: Jonathan Dowland <[email protected]>

modules/maven/default/module.yaml

@@ -31,11 +31,21 @@ envs:
 - name: MAVEN_CLEAR_REPO
   description: If set then the Maven repository is removed after the artifact is built. This is useful for keeping the created application image small, but prevents *incremental* builds. Will be overridden by **S2I_ENABLE_INCREMENTAL_BUILDS**.  Defaults to *false*.
 - name: MAVEN_MIRROR_URL
-  description: The base URL of a mirror used for retrieving artifacts.
+  description: >
+    The base URL of a mirror used for retrieving artifacts.
+    See `MAVEN_MIRRORS` for specifying multiple mirrors.
   example: "http://10.0.0.1:8080/repository/internal/"
 - name: MAVEN_MIRRORS
-  description: "If set, multi-mirror support is enabled, and other MAVEN_MIRROR_* variables will be prefixed. For example: DEV_ONE_MAVEN_MIRROR_URL and QE_TWO_MAVEN_MIRROR_URL"
-  example: "dev-one,qe-two"
+  description: >
+    Enables multi-mirror support. Specify a comma-delimited list of capitalized
+    mirror identifiers. The configuration for each mirror will be determined by
+    correspondingly prefixed `MAVEN_MIRROR_*` variables. Any dashes in mirror
+    names will be replaced by underscores. For example: Specifying
+    `DEV-ONE,QE-TWO` configures two mirrors and their URLs will be read from
+    the `DEV_ONE_MAVEN_MIRROR_URL` and `QE_TWO_MAVEN_MIRROR_URL` variables.
+    See also: `prefix_MAVEN_MIRROR_ID`; `prefix_MAVEN_MIRROR_OF`;
+    `prefix_MAVEN_MIRROR_URL`.
+  example: "DEV-ONE,QE-TWO"
 - name: prefix_MAVEN_MIRROR_ID
   description: "ID to be used for the specified mirror.  If omitted, a unique ID will be generated."
   example: "internal-mirror"