A new entry point for calling the cred helpers that allow passing environment variables

Signed-off-by: Peter Hsu <shhsu@microsoft.com>

client/command.go

@@ -1,6 +1,7 @@
 package client
 
 import (
+	"fmt"
 	"io"
 	"os"
 	"os/exec"
@@ -17,15 +18,26 @@ type ProgramFunc func(args ...string) Program
 
 // NewShellProgramFunc creates programs that are executed in a Shell.
 func NewShellProgramFunc(name string) ProgramFunc {
+	return NewShellProgramFuncWithEnv(name, nil)
+}
+
+// NewShellProgramFuncWithEnv creates programs that are executed in a Shell with environment variables
+func NewShellProgramFuncWithEnv(name string, env *map[string]string) ProgramFunc {
 	return func(args ...string) Program {
-		return &Shell{cmd: newCmdRedirectErr(name, args)}
+		return &Shell{cmd: createProgramCmdRedirectErr(name, args, env)}
 	}
 }
 
-func newCmdRedirectErr(name string, args []string) *exec.Cmd {
-	newCmd := exec.Command(name, args...)
-	newCmd.Stderr = os.Stderr
-	return newCmd
+func createProgramCmdRedirectErr(commandName string, args []string, env *map[string]string) *exec.Cmd {
+	programCmd := exec.Command(commandName, args...)
+	programCmd.Env = os.Environ()
+	if env != nil {
+		for k, v := range *env {
+			programCmd.Env = append(programCmd.Env, fmt.Sprintf("%s=%s", k, v))
+		}
+	}
+	programCmd.Stderr = os.Stderr
+	return programCmd
 }
 
 // Shell invokes shell commands to talk with a remote credentials helper.