Vcs: Add variables containing the Vcs name (Git, etc.) and topic

This allows to have the git branch names (or tags, etc.) in the
build path or to pass that information to scripts.

Task-number: QTCREATORBUG-10376
Change-Id: I151990bdc7b85abbb427b2afae220adb4e918f4f
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/vcsbase/vcsbaseconstants.h

@@ -49,6 +49,9 @@ const char VCS_ID_SUBVERSION[] = "J.Subversion";
 const char VCS_ID_PERFORCE[] = "P.Perforce";
 const char VCS_ID_CVS[] = "Z.CVS";
 
+const char VAR_VCS_NAME[] = "CurrentProject:VcsName";
+const char VAR_VCS_TOPIC[] = "CurrentProject:VcsTopic";
+
 } // namespace Constants
 } // namespace VcsBase