Executing a git command using remote powershell results in a NativeCommmandError

Question

I am getting an error while executing a remote PowerShell script. From my local machine I am running a PowerShell script that uses Invoke-Command to cd into a directory on a remote Amazon Windows Server instance, and a subsequent Invoke-Command to execute script that lives on that server instance. The script on the server is trying to git clone a repository from GitHub. I can successfully do things in the server script like "ls" or even "git --version". However git clone, git pull, etc. result in the following error:

Cloning into 'MyRepo'... + CategoryInfo : NotSpecified: (Cloning into 'MyRepo'...:String) [], RemoteException + FullyQualifiedErrorId : NativeCommandError

This is my first time using PowerShell or a Windows Server. Can anyone provide some direction on this problem.

The client script:

$s = new-pssession -computername $server -credential $user
invoke-command -session $s -scriptblock { cd C:\Repos; ls } 
invoke-command -session $s -scriptblock { param ($repo, $branch) & '.\clone.ps1' -repository $repo -branch $branch} -ArgumentList $repository, $branch
exit-pssession

The server script:

param([string]$repository = "repository", [string]$branch = "branch")
git --version
start-process -FilePath git -ArgumentList ("clone", "-b $branch    https://github.com/MyGithub/$repository.git") -Wait 

I've changed the server script to use start process and it is no longer throwing the exception. It creates the new repository directory and the .git directory but doesn't write any of the files from the github repository. This smells like a permissions issue. Once again invoking the script manually (remote desktop into the amazon box and execute it from powershell) works like a charm.

Answer 1

As far as Powershell is concerned, it is the correct behaviour.

Unfortunately (at least in my opinon), git outputs a lot of information to stderr even when there isn't any error. For example git checkout -b somenewbranch will output things like modified file lists to stdout but the Switched to new branch somenewbranch message (which I think is the most relevant one) to stderr.

One of the most common ways to deal with this is to redirect stderr output to stdout, e.g:

git rebase master 2>&1

This is enough for most use cases I've seen. If you want to do something with the textual output itself you'll need to go a bit further as Powershell will store the stderr-originating lines as a RemoteException instead of a string. A brief example of how you might deal with something that needs to log output to the console:

$result  = Invoke-Expression "& git checkout -b somefeaturebranch 2>&1"

$output = ""
foreach($line in $result)
{
    $val = ""
    if($line.GetType().Name -eq "ErrorRecord")
    {        
        $val = $line.Exception.Message
    }else{
        $val = $line
    }   
    $output = "$output`r`n$val"
}

Write-Host $output

Answer 2

I see this 'error' as well when using Powershell ISE and Git locally. It isn't actually an error; rather, Powershell ISE is incorrectly interpreting Git's console output. If you try the console-based Powershell, you should notice that there is no error information displayed. It seems that this is just a peculiarity of Powershell ISE (and possibly other Powershell hosts that don't handle console application output well).

Answer 3

You may be running into Double Hop problem explained here: http://blogs.msdn.com/b/clustering/archive/2009/06/25/9803001.aspx