Answer to @wddgit question in form of a FAQ.

Author: ktf

FAQ.md

@@ -0,0 +1,24 @@
+## How can I tell which version of an external is used?
+
+First lookup your release in [config.map](https://github.com/cms-sw/cms-bot/blob/master/config.map).
+
+Each line contains properties of a release queue.
+
+`CMSDIST_TAG` will tell you which CMSDIST tag / branch to lookup in:
+
+<https://github.com/cms-sw/cmsdist>
+
+Look up for the spec related to your external and you should find in the first
+rows either a line of the kind:
+
+    Source: <some-url>
+
+for example:
+
+    Source: git+https://github.com/%github_user/root.git?obj=%{branch}/%{tag}&export=%{n}-%{realversion}&output=/%{n}-%{realversion}-%{tag}.tgz
+
+the `%{defined-variable}` gets expanded to their value, as required by rpm. In particular in many cases we have:
+
+- `%tag`: the hash commit to be used for the external.
+- `%branch`: the branch on which the commit its located.
+- `github_user`: the user owning the repository to be used.

README.md

@@ -29,6 +29,9 @@ through a Github issue.
 - [upload-release](): script used to upload a release to the repository. When
 the job processing build requests spots a request to upload, it SSH to the
 build machine which has the release and executes this script.
+- [config.map](https://github.com/cms-sw/cms-bot/blob/master/config.map): semicolon separated `key=value`
+pairs formatted file with release queue related information. Each line represent a release queue. In
+particular `CMSDIST_TAG` is used to point to the CMSDIST tag to be used by the release building process.
 
 # Logging