Merge pull request #707 from nils-a/feature/GH-702

(GH-702) added documentation for TeamCity

docs/input/docs/ci-systems/teamcity.md

@@ -4,4 +4,59 @@ Title: TeamCity
 Description: Running on TeamCity
 ---
 
-This documentation is currently missing. 
+## Specifics
+
+* `vcsroot.branch`-environment variable
+
+  Exposing the `vcsroot.branch` parameter as an environment variable is required.
+
+## Example Config
+
+Generally, TeamCity is configured using the UI:
+
+* Add a new build configuration to your project
+* Select a VCS-Root
+* Chose "configure build steps manually" (and skip auto-detection)
+* Select "PowerShell" as Runner type 
+* Add `build.ps1` as "Script file" and optionally some "Script arguments"
+
+  ![build.ps1 in script file](./teamcity/build-step.png){.img-responsive}
+* Select "Parameters" and a new parameter
+  * chose `env.vcsroot.branch` as Name,
+  * "Environment Variable" as Kind,
+  * `%vcsroot.branch%` as Value
+
+  ![env.vscroot.brach variable](./teamcity/parameter.png){.img-responsive}
+* At this point you are done with the basic setup and can select "Run" to try the new configuration.
+
+The following code shows the Kotlin DSL, as can be exported in TeamCity-UI. 
+Though generally the build is configured using the TeamCity-UI.
+
+```java
+object Cake : BuildType({
+    name = "Cake"
+
+    params {
+        param("env.vcsroot.branch", "%vcsroot.branch%")
+    }
+
+    vcs {
+        root(SomeConfiguredVcsRoot)
+    }
+
+    steps {
+        powerShell {
+            scriptMode = file {
+                path = "build.ps1"
+            }
+            noProfile = false
+            param("jetbrains_powershell_scriptArguments", "--verbosity=Diagnostic")
+        }
+    }
+
+    triggers {
+        vcs {
+        }
+    }
+})
+```