Prompts and Directories - Even Better Git (and Mercurial) with PowerShell

I love PowerShell and spent years and years working with it since it first came out. I've actually got 15 or so pages of PowerShell posts on this blog going way back.

PowerShell is insanely powerful. I would even go so far as to say it was (is) ahead of its time. PowerShell is totally dynamic and is almost like having JavaScript at the command line, but even more thoughtfully designed. I appreciate folks that love their bash shells and what not, but PowerShell can do some wonderful things.

A long time ago (2009) Mark Embling blogged about a nice prompt with TabExpansion that he'd made to make working with PowerShell and Git (his favorite source control system) nicer. Later, Jeremy Skinner added TabExpansion for common commands. A little while later Keith Dahlby started with their code (with their blessing) and posh-git was born. Expanding even more, Jeremy later created posh-hg (for Mercurial, my favorite source control system).

All of these are currently in use in various forms. Just recently (days ago, even) while I was trying figure out how to get these two separate but similar PowerShell scripts to live together when Keith created a small shared function that makes sharing prompts easier.

I think that Git Bash on Windows needs to go away. It's just not useful. PowerShell with Git (or your favorite VCS) is demonstrably better for Windows folks. I also feel that the installation for posh-git, while it uses PsGet (think NuGet for PowerShell, which is INSANELY awesome), just could be easier.

I happened to be tweeting about this and ended up doing a Skype+Join.me 3-way pair programming session with Keith and Paul Betts to explore some ideas on the topic. While a customized prompt is cool, I wouldn't rest until we'd modified "dir/ls" to show source control status. I'm not talking about a PowerShell Provider, I'm talking about extending the View for the result of a dir (get-childitem and a FileInfo) itself.

I want to be able to take a fresh machine and fresh PowerShell installation, invoke one PsGet command and get Git and Hg (and whoever else) integration with PowerShell, a new prompt AND new (yet to be written at this point) directory listing support.

We did some pairing as I sat in a pub and drove while Keith and Paul told me I was a lousy typist. We got a nice prototype working and I went home. After the kids went to sleep I was asking questions on a mailing list and ended up getting an answer from James Brundage, noted PowerShell expert. I'd met James at a Nerd Dinner in Seattle once and gave him a book. He was kind enough to do a screen sharing session with me and refactor my directory spike (and some of posh-git) into a more useful form. It's still a spike, but Keith and I are going to merge all three of them (posh-git, posh-hg and my VCS dir stuff) into one usable and easy to install module. I'm sure we'll both blog about it when it's cleaner. I'm hoping we'll get it all integrated into a single install line:

(new-object Net.WebClient).DownloadString("http://psget.net/GetPsGet.ps1") | iex
install-module posh-git

Here's the general idea that encapsulates a number of these ideas. Rather than scripts that are plugged into your PowerShell $profile, we'll have a module or two like this.

C:\Users\Scott\Documents\WindowsPowerShell\Modules
$ dir

Mode         LastWriteTime   Length Name
----         -------------   ------ ----
d----  1/31/2012  10:37 PM          Posh-Git
d----  1/31/2012  10:37 PM          Posh-GitDir
d----  1/31/2012  12:27 AM          PsGet

The Posh-Git folder is the Posh-Git source as it is, as a module and imported in your profile like this.

Import-Module Posh-Git
Import-Module Posh-GitDir

Posh-GitDir is my extension module that will change dir/ls/get-childitem and add a Git Status column. I've added extra columns with file information before in PowerShell, except in a cheesy way and I never actually overrode dir directly.

First, we'll make a post-gitdir.Types.ps1xml that adds the new ScriptProperty that pulls details for each file out of a $GitStatus variable that's added each time the prompt is drawn.

<?xml version="1.0" encoding="utf-8" ?>
<Types>
     <Type>
        <Name>System.IO.FileInfo</Name>
        <Members>
            <ScriptProperty>
                <Name>Git</Name>
                <GetScriptBlock>
                $retVal = ""
                if ($GitStatus.Index.Added -contains $this.Name) {  $retVal += "+" } `
                elseif ($GitStatus.Index.Modified -contains $this.Name) { $retVal += "~" } `
                elseif ($GitStatus.Index.Unmerged -contains $this.Name) { $retVal += "!" } `
                else { $retVal +=  " " }

                $retVal +=  " "
                
                if ($GitStatus.Working.Added -contains $this.Name) { $retVal += "+" } `
                elseif ($GitStatus.Working.Modified -contains $this.Name) { $retVal += "~" } `
                elseif ($GitStatus.Working.Unmerged -contains $this.Name) { $retVal += "!" } `
                else { $retVal += " " }

                $retVal 
                </GetScriptBlock>
            </ScriptProperty>
          </Members>
     </Type>
     <Type>
        <Name>System.IO.DirectoryInfo</Name>
        <Members>
           <ScriptProperty>
                <Name>Git</Name>
                <GetScriptBlock>
                ""
                </GetScriptBlock>
            </ScriptProperty>
          </Members>
     </Type>
</Types>

This adds the Git column to the output as a ScriptProperty, but doesn't change the default view.

$ dir | get-member

   TypeName: Get-ChildItem

Name                      MemberType     Definition
----                      ----------     ----------
Mode                      CodeProperty   System.String Mode{get=Mode;}
Create                    Method         System.Void Create(System.Security.AccessControl.DirectorySecurity director...
CreateObjRef              Method         System.Runtime.Remoting.ObjRef CreateObjRef(type requestedType)
...snip...
BaseName                  ScriptProperty System.Object BaseName {get=$this.Name;}
Git                       ScriptProperty System.Object Git {get="";}

I'd have to always select manually, which is tedious.

$ dir | select Name, Git

Name                        Git
----                        ---
CommandType.cs                ~
Connection.cs                 ~
ConnectionExtensions.cs       ~
ConnectionManager.cs        +
ConnectionScope.cs            +
GuidConnectionIdFactory.cs    ~

We want to change the dir "view" itself.  We have to copy the default view for a directory at: "C:\Windows\system32\WindowsPowerShell\v1.0\FileSystem.format.ps1xml" and add our new column.

<?xml version="1.0" encoding="utf-16"?>
<Configuration>
  <ViewDefinitions>
    <View>
      <Name>Dir-Git</Name>
      <ViewSelectedBy>
        <TypeName>Dir-Git</TypeName>
      </ViewSelectedBy>
      <TableControl>
                <TableHeaders>
                   <TableColumnHeader>
                      <Label>Git</Label>
                      <Width>4</Width>
                      <Alignment>left</Alignment>
                   </TableColumnHeader>
...snip...
                </TableHeaders>
                <TableRowEntries>
                    <TableRowEntry>
                        <Wrap/>
                        <TableColumnItems>
                            <TableColumnItem>
                              <PropertyName>Git</PropertyName>
                            </TableColumnItem>
...snip...
                        </TableColumnItems>
                    </TableRowEntry>
                </TableRowEntries>
            </TableControl>
    </View>
  </ViewDefinitions>
</Configuration>

For the design, I want the Indexed and Working files in two columns, showing Added+, Modified~ and Unmerged! files like this. Deleted files won't show up cause they aren't there.

$ dir #snipped out directories and files for clarity

Mode  Git         LastWriteTime     Length Name
----  ---         -------------     ------ ----
d----       1/31/2012   5:14 PM            Configuration
d----       1/31/2012   5:14 PM            Hosting
-a---   +   1/31/2012   5:14 PM       2170 ConnectionManager.cs
-a---   +   1/31/2012   5:14 PM        402 ConnectionScope.cs
-a---   ~   1/31/2012   5:14 PM        280 GuidConnectionIdFactory.cs
-a---       1/31/2012   5:14 PM        273 IConnection.cs
-a---   ~   1/31/2012   5:14 PM        165 IConnectionIdFactory.cs
-a---   +   1/31/2012   5:14 PM        304 IConnectionManager.cs
-a---       1/31/2012   5:14 PM        118 packages.config
-a---   ~   1/31/2012   5:14 PM       8296 PersistentConnection.cs
-a--- +     1/31/2012   5:14 PM       1118 PersistentConnectionFactory.cs
-a---       1/31/2012   5:14 PM        623 PersistentResponse.cs
-a---   ~   1/31/2012   5:14 PM       1288 SignalCommand.cs
-a---   ~   1/31/2012   5:14 PM       7386 SignalR.csproj
-a---       1/31/2012   5:14 PM      23076 TaskAsyncHelper.cs

C:\Users\Scott\Desktop\github\SignalR\SignalR [master +1 ~0 -0 | +10 ~58 -11 !]

We import these modules in our $profile.

Import-Module Posh-Git
Import-Module Posh-GitDir

The posh-git module adds the custom prompt (if you haven't changed yours) with a new function called Write-VcsStatus that is shared between Hg and Git (and any other systems that want to play with us). It only adds the prompt if the user hasn't already customized their prompt. If they have, they'll need to incorporate Write-VcsStatus themselves.

$defaultPromptHash = "HEYStcKFSSj9jrfqnb9f+A=="

$md5 = [Security.Cryptography.MD5]::Create()
$thePrompt = [Text.Encoding]::Unicode.GetBytes((Get-Command prompt | Select-Object -ExpandProperty Definition))
$thePromptHash = [Convert]::ToBase64String($md5.ComputeHash($thePrompt))

if ($thePromptHash -eq $defaultPromptHash) #using the default prompt?
{
    #recommend our own
    function prompt(){
        # Reset color, which can be messed up by Enable-GitColors
        $Host.UI.RawUI.ForegroundColor = $GitPromptSettings.DefaultForegroundColor

        Write-Host($pwd) -nonewline -foregroundcolor white

        Write-VcsStatus 

        Write-Host ""
        return "$ "
    }
}
else {
    Write-Debug "Make sure your prompt includes a called to Write-VcsStatus!"    
}

The craziness that James Brundage came up with to override dir/ls/get-childitem was this. He said he'll do a complete tutorial on his blog with technical details for the generic case.

. ([ScriptBlock]::Create("
function Get-ChildItem {
    $([Management.Automation.ProxyCommand]::GetCmdletBindingAttribute((Get-Command Get-ChildItem -CommandType Cmdlet)))
    param(
    $([Management.Automation.ProxyCommand]::GetParamBlock((Get-Command Get-ChildItem -CommandType Cmdlet)))
    )
    
    process {
        Microsoft.PowerShell.Management\Get-ChildItem @psBoundParameters |
            ForEach-Object {
                `$null = `$_.pstypenames.Insert(0, 'Dir-Git')
                `$_
            }
    }
}
"))

Tie it all up with a .psd1 file that has the list of Scripts, Types, Formats and the Module.

@{
    ModuleVersion="1.0.0.0"
    Author="Scott Hanselman"
    Description="Posh-GitDir"
    CompanyName="Hanselman and Friends"
    RequiredModules="Posh-Git"
    ScriptsToProcess="prompt.ps1"
    TypesToProcess="posh-gitdir.Types.ps1xml"
    FormatsToProcess="posh-gitdir.Format.ps1xml"
    ModuleToProcess="posh-gitdir.psm1"
}

To recap, this new module requires the posh-git module, it ands our new "Dir-Git" type, adds the Git ScriptProperty in Types, and shows how to Format it, and overrides get-childitem in the psm1. If you didn't want to override dir proper, maybe you could make a dir-git or dir-hg.

Next steps are for us to integrate them into one module, bring in an inproc library to access the source info (rather than regex'ing the output of git status and hg status) which would speed it up 10x I'm sure, as well as better NuGet support.

In this screenshot you can see posh-git and posh-hg living together. The first directory is a hg repo with a 1 file not in control. The second directory is a git repo with 1 file added in the Index, 10 new added in working, 58 modified, and 11 deleted.

Keith and Jeremy have done some amazing work. Open Source, baby. I'm looking forward to pairing with them in coming days and buttoning this up. I've been a hardcore Tortoise (Tortoise-Hg, Tortoise-SVN, Tortoise-Git) source control user, but the addition of PowerShell is shaking my faith in a good way. At leat to the point that I think it's worth my spare time to see this through.

Thoughts?

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