Extract build server environment variable names to constants

Author: eatdrinksleepcode

src/GitVersionCore.Tests/ExecuteCoreTests.cs

@@ -141,8 +141,8 @@ public void DynamicRepositoriesShouldNotErrorWithFailedToFindGitDirectory()
     string RepositoryScope(ExecuteCore executeCore = null, Action<EmptyRepositoryFixture, VersionVariables> fixtureAction = null)
     {
         // Make sure GitVersion doesn't trigger build server mode when we are running the tests
-        Environment.SetEnvironmentVariable("APPVEYOR", null);
-		Environment.SetEnvironmentVariable("TRAVIS", null);
+		Environment.SetEnvironmentVariable(AppVeyor.EnvironmentVariableName, null);
+		Environment.SetEnvironmentVariable(TravisCI.EnvironmentVariableName, null);
         var infoBuilder = new StringBuilder();
         Action<string> infoLogger = s =>
         {

src/GitVersionCore/BuildServers/AppVeyor.cs

@@ -6,9 +6,11 @@
 
     public class AppVeyor : BuildServerBase
     {
-        public override bool CanApplyToCurrentContext()
+		public const string EnvironmentVariableName = "APPVEYOR";
+
+		public override bool CanApplyToCurrentContext()
         {
-            return !string.IsNullOrEmpty(Environment.GetEnvironmentVariable("APPVEYOR"));
+			return !string.IsNullOrEmpty(Environment.GetEnvironmentVariable(EnvironmentVariableName));
         }
 
         public override string GenerateSetVersionMessage(VersionVariables variables)

src/GitVersionCore/BuildServers/TeamCity.cs

@@ -4,9 +4,11 @@
 
     public class TeamCity : BuildServerBase
     {
-        public override bool CanApplyToCurrentContext()
+		public const string EnvironmentVariableName = "TEAMCITY_VERSION";
+
+		public override bool CanApplyToCurrentContext()
         {
-            return !string.IsNullOrEmpty(Environment.GetEnvironmentVariable("TEAMCITY_VERSION"));
+			return !string.IsNullOrEmpty(Environment.GetEnvironmentVariable(EnvironmentVariableName));
         }
 
         public override string GetCurrentBranch(bool usingDynamicRepos)

src/GitVersionCore/BuildServers/TravisCI.cs

@@ -3,9 +3,11 @@ namespace GitVersion
 {
 	public class TravisCI : BuildServerBase
 	{
+		public const string EnvironmentVariableName = "TRAVIS";
+
 		public override bool CanApplyToCurrentContext ()
 		{
-			return "true".Equals(Environment.GetEnvironmentVariable ("TRAVIS")) && "true".Equals(Environment.GetEnvironmentVariable("CI"));
+			return "true".Equals(Environment.GetEnvironmentVariable(EnvironmentVariableName)) && "true".Equals(Environment.GetEnvironmentVariable("CI"));
 		}
 
 		public override string GenerateSetVersionMessage(VersionVariables variables)

src/GitVersionExe.Tests/GitVersionHelper.cs

@@ -3,6 +3,7 @@
 using System.IO;
 using System.Text;
 using GitTools;
+using GitVersion;
 
 public static class GitVersionHelper
 {
@@ -36,9 +37,9 @@ static ExecutionResults ExecuteIn(ArgumentBuilder arguments)
         var environmentalVariables =
             new[]
             {
-                new KeyValuePair<string, string>("TEAMCITY_VERSION", arguments.IsTeamCity ? "8.0.0" : null),
-                new KeyValuePair<string, string>("APPVEYOR", null),
-				new KeyValuePair<string, string>("TRAVIS", null),
+				new KeyValuePair<string, string>(TeamCity.EnvironmentVariableName, arguments.IsTeamCity ? "8.0.0" : null),
+				new KeyValuePair<string, string>(AppVeyor.EnvironmentVariableName, null),
+				new KeyValuePair<string, string>(TravisCI.EnvironmentVariableName, null),
 			};
 
         var exitCode = -1;