ProcessHelper: account for platform differences in program locater

Currently, this is hardcoded to run the "where" program, which is not
appropriate on non-Windows platforms. Add a platform abstraction so different
platforms can run different programs.

GVFS/GVFS.Common/GVFSPlatform.cs

@@ -106,6 +106,8 @@ namespace GVFS.Common
 
             public abstract string GVFSExecutableName { get; }
 
+            public abstract string ProgramLocaterCommand { get; }
+
             public string GVFSHooksExecutableName
             {
                 get { return "GVFS.Hooks" + this.ExecutableExtension; }

GVFS/GVFS.Common/InstallerPreRunChecker.cs

@@ -153,7 +153,7 @@ namespace GVFS.Upgrader
 
         protected virtual bool TryRunGVFSWithArgs(string args, out string consoleError)
         {
-            string gvfsDirectory = ProcessHelper.WhereDirectory(GVFSPlatform.Instance.Constants.GVFSExecutableName);
+            string gvfsDirectory = ProcessHelper.GetProgramLocation(GVFSPlatform.Instance.Constants.ProgramLocaterCommand, GVFSPlatform.Instance.Constants.GVFSExecutableName);
             if (!string.IsNullOrEmpty(gvfsDirectory))
             {
                 string gvfsPath = Path.Combine(gvfsDirectory, GVFSPlatform.Instance.Constants.GVFSExecutableName);

GVFS/GVFS.Common/ProcessHelper.cs

@@ -62,9 +62,9 @@ namespace GVFS.Common
             return currentVersion.Major == 0;
         }
 
-        public static string WhereDirectory(string processName)
+        public static string GetProgramLocation(string programLocaterCommand, string processName)
         {
-            ProcessResult result = ProcessHelper.Run("where", processName);
+            ProcessResult result = ProcessHelper.Run(programLocaterCommand, processName);
             if (result.ExitCode != 0)
             {
                 return null;

GVFS/GVFS.PerfProfiling/ProfilingEnvironment.cs

@@ -26,7 +26,7 @@ namespace GVFS.PerfProfiling
         private GVFSEnlistment CreateEnlistment(string enlistmentRootPath)
         {
             string gitBinPath = GVFSPlatform.Instance.GitInstallation.GetInstalledGitBinPath();
-            string hooksPath = ProcessHelper.WhereDirectory(GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);
+            string hooksPath = ProcessHelper.GetProgramLocation(GVFSPlatform.Instance.Constants.ProgramLocaterCommand, GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);
 
             return GVFSEnlistment.CreateFromDirectory(enlistmentRootPath, gitBinPath, hooksPath, authentication: null);
         }

GVFS/GVFS.Platform.POSIX/POSIXPlatform.cs

@@ -199,6 +199,12 @@ namespace GVFS.Platform.POSIX
             {
                 get { return "gvfs"; }
             }
+
+            public override string ProgramLocaterCommand
+            {
+                get { return "which"; }
+            }
+
         }
     }
 }

GVFS/GVFS.Platform.Windows/WindowsGitInstallation.cs

@@ -19,7 +19,7 @@ namespace GVFS.Platform.Windows
                 return File.Exists(gitBinPath);
             }
 
-            return ProcessHelper.WhereDirectory(GitProcessName) != null;
+            return ProcessHelper.GetProgramLocation(GVFSPlatform.Instance.Constants.ProgramLocaterCommand, GitProcessName) != null;
         }
 
         public string GetInstalledGitBinPath()
@@ -37,4 +37,4 @@ namespace GVFS.Platform.Windows
             return null;
         }
     }
-}
+}

GVFS/GVFS.Platform.Windows/WindowsPlatform.cs

@@ -244,7 +244,7 @@ namespace GVFS.Platform.Windows
         {
             error = null;
             hooksVersion = null;
-            hooksPath = ProcessHelper.WhereDirectory(GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);
+            hooksPath = ProcessHelper.GetProgramLocation(GVFSPlatform.Instance.Constants.ProgramLocaterCommand, GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);
             if (hooksPath == null)
             {
                 error = "Could not find " + GVFSPlatform.Instance.Constants.GVFSHooksExecutableName;
@@ -447,6 +447,11 @@ namespace GVFS.Platform.Windows
             {
                 get { return "GVFS" + this.ExecutableExtension; }
             }
+
+            public override string ProgramLocaterCommand
+            {
+                get { return "where"; }
+            }
         }
     }
 }

GVFS/GVFS.UnitTests/Mock/Common/MockPlatform.cs

@@ -201,6 +201,11 @@ namespace GVFS.UnitTests.Mock.Common
             {
                 get { return "MockGVFS" + this.ExecutableExtension; }
             }
+
+            public override string ProgramLocaterCommand
+            {
+                get { return "MockWhere"; }
+            }
         }
     }
 }

GVFS/GVFS/CommandLine/GVFSVerb.cs

@@ -1110,7 +1110,7 @@ You can specify a URL, a name of a configured cache server, or the special names
                     // the .git/hooks folder, and once Windows does the same, this hooksPath can be removed (from here
                     // and all the classes that handle it on the way to GitProcess)
 
-                    hooksPath = ProcessHelper.WhereDirectory(GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);
+                    hooksPath = ProcessHelper.GetProgramLocation(GVFSPlatform.Instance.Constants.ProgramLocaterCommand, GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);
                     if (hooksPath == null)
                     {
                         this.ReportErrorAndExit("Could not find " + GVFSPlatform.Instance.Constants.GVFSHooksExecutableName);