Pass SSH_AUTH_SOCK variable for ssh authentication while cloning repo…

Sources/Get/Git.swift

@@ -10,6 +10,7 @@
 
 import struct PackageDescription.Version
 import func POSIX.realpath
+import func POSIX.getenv
 import enum POSIX.Error
 import Utility
 
@@ -22,10 +23,18 @@ extension Git {
         }
 
         do {
+            //List of environment variables which might be useful while running git
+            let environmentList = ["SSH_AUTH_SOCK", "GIT_ASKPASS", "SSH_ASKPASS", "XDG_CONFIG_HOME"
+                , "LANG", "LANGUAGE", "EDITOR", "PAGER", "TERM"]
+            let environment = environmentList.reduce([String:String]()) { (accum, env) in
+                var newAccum = accum
+                newAccum[env] = getenv(env)
+                return newAccum
+            }
             try system(Git.tool, "clone",
                        "--recursive",   // get submodules too so that developers can use these if they so choose
                 "--depth", "10",
-                url, dstdir, message: "Cloning \(url)")
+                url, dstdir, environment: environment, message: "Cloning \(url)")
         } catch POSIX.Error.ExitStatus {
             throw Error.GitCloneFailure(url, dstdir)
         }

Sources/Utility/Verbosity.swift

@@ -87,19 +87,19 @@ import func libc.fflush
 import var libc.stdout
 import enum POSIX.Error
 
-public func system(arguments: String..., message: String?) throws {
+public func system(arguments: String..., environment: [String:String] = [:], message: String?) throws {
     var out = ""
     do {
         if Utility.verbosity == .Concise {
             if let message = message {
                 print(message)
                 fflush(stdout)  // ensure we display `message` before git asks for credentials
             }
-            try POSIX.popen(arguments, redirectStandardError: true) { line in
+            try POSIX.popen(arguments, redirectStandardError: true, environment: environment) { line in
                 out += line
             }
         } else {
-            try system(arguments)
+            try system(arguments, environment: environment)
         }
     } catch POSIX.Error.ExitStatus(let foo) {
         if verbosity == .Concise {