List the platforms that we currently support. Document staging.repository.

protoc-artifacts/README.md

@@ -56,7 +56,12 @@ configure GPG and Sonatype account.
 
 You need to perform the deployment for every platform that you want to
 suppport. DO NOT close the staging repository until you have done the
-deployment for all platforms.
+deployment for all platforms. Currently the following platforms are supported:
+- Linux (x86_32 and x86_64)
+- Windows (x86_32 and x86_64) with
+ - Cygwin with MinGW compilers (both x86_32 and x86_64)
+ - MSYS with MinGW32 (x86_32 only)
+- MacOSX (x86_32 and x86_64)
 
 Remove any ``SNAPSHOT`` or ``pre`` suffix from the version string before
 deploying.

protoc-artifacts/pom.xml

@@ -91,6 +91,11 @@
     <profile>
       <id>release</id>
       <properties>
+        <!-- Specify the staging repository to deploy to. This can be left
+             empty for the first deployment, and Sonatype will create one. For
+             subsequent deployments it should be set to what Sonatype has
+             created, so that all deployments will go to the same repository.
+             -->
         <staging.repository></staging.repository>
       </properties>
       <build>