initial code to show how async 'git status' prompt can work

GitAsyncPrompt.ps1

@@ -0,0 +1,220 @@
+function Write-GitStatusPromptAsync([string]$gitDir = (Get-GitDirectory)) {
+    $processStartInfo = New-Object Diagnostics.ProcessStartInfo
+    $processStartInfo.FileName = "git"
+    $processStartInfo.Arguments = "-c color.status=false status --short --branch"
+    $processStartInfo.CreateNoWindow = $true
+    $processStartInfo.RedirectStandardOutput = $true
+    $processStartInfo.RedirectStandardError = $false
+    $processStartInfo.UseShellExecute = $false
+    $processStartInfo.WorkingDirectory = $pwd.ProviderPath
+
+    $process = New-Object Diagnostics.Process
+    $process.StartInfo = $processStartInfo
+
+    $processOutputLines = @()
+    $positionToWriteStatus = $Host.UI.RawUI.CursorPosition
+
+    # Output a placeholder line where the status will be written to.  This makes sure the status line doesn't overwrite the actual prompt
+    Write-Host " [...]" 
+
+    $messageData = new-object psobject -property @{
+        gitDir = $gitDir
+        processOutputLines = $processOutputLines
+        positionToWriteStatus = $positionToWriteStatus
+    }
+
+    Register-ObjectEvent -InputObject $process -EventName OutputDataReceived -MessageData $messageData -action {
+        $event.MessageData.processOutputLines += $EventArgs.data
+    } | Out-Null
+    Register-ObjectEvent -InputObject $process -EventName Exited -MessageData $messageData -action {
+        $gitStatusObject = Convert-GitStatusOutput $event.MessageData.processOutputLines $event.MessageData.gitDir
+
+        # to maintain behavior compatibility with synchronous prompt, set the global GitStatus variable
+        $global:GitStatus = $gitStatusObject
+
+        $bufferCells = Get-GitStatusBufferCells $gitStatusObject
+        Write-BufferCellsToPosition $bufferCells $event.MessageData.positionToWriteStatus
+    } | Out-Null
+
+    $process.Start() | Out-Null
+    $process.BeginOutputReadLine()
+}
+
+function New-BufferCells([string] $content, [consolecolor] $ForegroundColor, [consolecolor] $BackgroundColor) {
+    if ($content) {
+        $Host.UI.RawUI.NewBufferCellArray($content, $ForegroundColor, $BackgroundColor)
+    }
+}
+
+function Write-BufferCellsToPosition([System.Management.Automation.Host.BufferCell[]] $bufferCells, [System.Management.Automation.Host.Coordinates] $position) {
+    # SetBufferContents needs the cells as a 2-dimensional array (not a jagged array), so we have to create one
+    $bufferCells2d = new-object 'System.Management.Automation.Host.BufferCell[,]' 1, $bufferCells.Length
+    foreach ($index in 0 .. $($bufferCells.Length - 1)) {
+        $bufferCells2d[0,$index] = $bufferCells[$index]
+    }
+
+    $host.UI.RawUI.SetBufferContents($position, $bufferCells2d)
+}
+
+function Get-GitStatusBufferCells([psobject] $status) {
+    $s = $global:GitPromptSettings
+    if ($status -and $s) {
+        # initial set of buffer cells set here, so don't use +=
+        #[System.Management.Automation.Host.BufferCell[,]] 
+        $bufferCells = New-BufferCells $s.BeforeText -BackgroundColor $s.BeforeBackgroundColor -ForegroundColor $s.BeforeForegroundColor
+
+        $branchBackgroundColor = $s.BranchBackgroundColor
+        $branchForegroundColor = $s.BranchForegroundColor
+        if ($status.BehindBy -gt 0 -and $status.AheadBy -gt 0) {
+            # We are behind and ahead of remote
+            $branchBackgroundColor = $s.BranchBehindAndAheadBackgroundColor
+            $branchForegroundColor = $s.BranchBehindAndAheadForegroundColor
+        } elseif ($status.BehindBy -gt 0) {
+            # We are behind remote
+            $branchBackgroundColor = $s.BranchBehindBackgroundColor
+            $branchForegroundColor = $s.BranchBehindForegroundColor
+        } elseif ($status.AheadBy -gt 0) {
+            # We are ahead of remote
+            $branchBackgroundColor = $s.BranchAheadBackgroundColor
+            $branchForegroundColor = $s.BranchAheadForegroundColor
+        }
+
+        $bufferCells += New-BufferCells $status.Branch -BackgroundColor $branchBackgroundColor -ForegroundColor $branchForegroundColor
+
+        if($s.EnableFileStatus -and $status.HasIndex) {
+            $bufferCells += New-BufferCells $s.BeforeIndexText -BackgroundColor $s.BeforeIndexBackgroundColor -ForegroundColor $s.BeforeIndexForegroundColor
+
+            if($s.ShowStatusWhenZero -or $status.Index.Added) {
+              $bufferCells += New-BufferCells " +$($status.Index.Added.Count)" -BackgroundColor $s.IndexBackgroundColor -ForegroundColor $s.IndexForegroundColor
+            }
+            if($s.ShowStatusWhenZero -or $status.Index.Modified) {
+              $bufferCells += New-BufferCells " ~$($status.Index.Modified.Count)" -BackgroundColor $s.IndexBackgroundColor -ForegroundColor $s.IndexForegroundColor
+            }
+            if($s.ShowStatusWhenZero -or $status.Index.Deleted) {
+              $bufferCells += New-BufferCells " -$($status.Index.Deleted.Count)" -BackgroundColor $s.IndexBackgroundColor -ForegroundColor $s.IndexForegroundColor
+            }
+
+            if ($status.Index.Unmerged) {
+                $bufferCells += New-BufferCells " !$($status.Index.Unmerged.Count)" -BackgroundColor $s.IndexBackgroundColor -ForegroundColor $s.IndexForegroundColor
+            }
+
+            if($status.HasWorking) {
+                $bufferCells += New-BufferCells $s.DelimText -BackgroundColor $s.DelimBackgroundColor -ForegroundColor $s.DelimForegroundColor
+            }
+        }
+
+        if($s.EnableFileStatus -and $status.HasWorking) {
+            if($s.ShowStatusWhenZero -or $status.Working.Added) {
+              $bufferCells += New-BufferCells " +$($status.Working.Added.Count)" -BackgroundColor $s.WorkingBackgroundColor -ForegroundColor $s.WorkingForegroundColor
+            }
+            if($s.ShowStatusWhenZero -or $status.Working.Modified) {
+              $bufferCells += New-BufferCells " ~$($status.Working.Modified.Count)" -BackgroundColor $s.WorkingBackgroundColor -ForegroundColor $s.WorkingForegroundColor
+            }
+            if($s.ShowStatusWhenZero -or $status.Working.Deleted) {
+              $bufferCells += New-BufferCells " -$($status.Working.Deleted.Count)" -BackgroundColor $s.WorkingBackgroundColor -ForegroundColor $s.WorkingForegroundColor
+            }
+
+            if ($status.Working.Unmerged) {
+                $bufferCells += New-BufferCells " !$($status.Working.Unmerged.Count)" -BackgroundColor $s.WorkingBackgroundColor -ForegroundColor $s.WorkingForegroundColor
+            }
+        }
+
+        if ($status.HasUntracked) {
+            $bufferCells += New-BufferCells $s.UntrackedText -BackgroundColor $s.UntrackedBackgroundColor -ForegroundColor $s.UntrackedForegroundColor
+        }
+
+        $bufferCells += New-BufferCells $s.AfterText -BackgroundColor $s.AfterBackgroundColor -ForegroundColor $s.AfterForegroundColor
+
+        # return full set of cells back to caller
+        $bufferCells
+    }
+}
+
+function ShouldRunAsyncGitStatus {
+    $shouldRunAsync =
+        $Global:GitPromptSettings -and
+        $Global:GitPromptSettings.EnablePromptStatus -and
+        $Global:GitPromptSettings.EnableFileStatus -and
+        $Global:GitPromptSettings.EnableAsyncFileStatus -and
+        (Get-GitDirectory) -and
+        -not $(InDisabledRepository)
+
+    return $shouldRunAsync
+}
+
+function Convert-GitStatusOutput([string[]] $status, [string]$gitDir) {
+    $branch = $null
+    $aheadBy = 0
+    $behindBy = 0
+    $indexAdded = @()
+    $indexModified = @()
+    $indexDeleted = @()
+    $indexUnmerged = @()
+    $filesAdded = @()
+    $filesModified = @()
+    $filesDeleted = @()
+    $filesUnmerged = @()
+
+    $status | foreach {
+        if($_) {
+            switch -regex ($_) {
+                '^(?<index>[^#])(?<working>.) (?<path1>.*?)(?: -> (?<path2>.*))?$' {
+                    switch ($matches['index']) {
+                        'A' { $indexAdded += $matches['path1'] }
+                        'M' { $indexModified += $matches['path1'] }
+                        'R' { $indexModified += $matches['path1'] }
+                        'C' { $indexModified += $matches['path1'] }
+                        'D' { $indexDeleted += $matches['path1'] }
+                        'U' { $indexUnmerged += $matches['path1'] }
+                    }
+                    switch ($matches['working']) {
+                        '?' { $filesAdded += $matches['path1'] }
+                        'A' { $filesAdded += $matches['path1'] }
+                        'M' { $filesModified += $matches['path1'] }
+                        'D' { $filesDeleted += $matches['path1'] }
+                        'U' { $filesUnmerged += $matches['path1'] }
+                    }
+                }
+
+                '^## (?<branch>\S+)(?:\.\.\.(?<upstream>\S+) \[(?:ahead (?<ahead>\d+))?(?:, )?(?:behind (?<behind>\d+))?\])?$' {
+                    $branch = $matches['branch']
+                    $upstream = $matches['upstream']
+                    $aheadBy = [int]$matches['ahead']
+                    $behindBy = [int]$matches['behind']
+                }
+
+                '^## Initial commit on (?<branch>\S+)$' {
+                    $branch = $matches['branch']
+                }
+            }
+        }
+    }
+
+    if(!$branch) { $branch = Get-GitBranch $gitDir $sw }
+    $indexPaths = $indexAdded + $indexModified + $indexDeleted + $indexUnmerged
+    $workingPaths = $filesAdded + $filesModified + $filesDeleted + $filesUnmerged
+    $index = New-Object PSObject @(,@($indexPaths | ?{ $_ } | Select -Unique)) |
+        Add-Member -PassThru NoteProperty Added    $indexAdded |
+        Add-Member -PassThru NoteProperty Modified $indexModified |
+        Add-Member -PassThru NoteProperty Deleted  $indexDeleted |
+        Add-Member -PassThru NoteProperty Unmerged $indexUnmerged
+    $working = New-Object PSObject @(,@($workingPaths | ?{ $_ } | Select -Unique)) |
+        Add-Member -PassThru NoteProperty Added    $filesAdded |
+        Add-Member -PassThru NoteProperty Modified $filesModified |
+        Add-Member -PassThru NoteProperty Deleted  $filesDeleted |
+        Add-Member -PassThru NoteProperty Unmerged $filesUnmerged
+
+    $gitStatusObject = New-Object PSObject -Property @{
+        GitDir          = $gitDir
+        Branch          = $branch
+        AheadBy         = $aheadBy
+        BehindBy        = $behindBy
+        HasIndex        = [bool]$index
+        Index           = $index
+        HasWorking      = [bool]$working
+        Working         = $working
+        HasUntracked    = [bool]$filesAdded
+    }
+
+    return $gitStatusObject
+}

GitPrompt.ps1

@@ -44,6 +44,7 @@ $global:GitPromptSettings = New-Object PSObject -Property @{
 
     EnablePromptStatus        = !$Global:GitMissing
     EnableFileStatus          = $true
+    EnableAsyncFileStatus     = $true
     RepositoriesInWhichToDisableFileStatus = @( ) # Array of repository paths
 
     EnableWindowTitle         = 'posh~git ~ '
@@ -151,6 +152,13 @@ function Global:Write-VcsStatus { $Global:VcsPromptStatuses | foreach { & $_ } }
 
 # Add scriptblock that will execute for Write-VcsStatus
 $Global:VcsPromptStatuses += {
-    $Global:GitStatus = Get-GitStatus
-    Write-GitStatus $GitStatus
+    if (ShouldRunAsyncGitStatus)
+    {
+        Write-GitStatusPromptAsync
+    }
+    else
+    {
+        $Global:GitStatus = Get-GitStatus
+        Write-GitStatus $GitStatus
+    }
 }

posh-git.psm1

@@ -6,6 +6,7 @@ Push-Location $psScriptRoot
 . .\Utils.ps1
 . .\GitUtils.ps1
 . .\GitPrompt.ps1
+. .\GitAsyncPrompt.ps1
 . .\GitTabExpansion.ps1
 . .\TortoiseGit.ps1
 Pop-Location
@@ -22,6 +23,12 @@ Export-ModuleMember `
     -Function @(
         'Invoke-NullCoalescing',
         'Write-GitStatus',
+
+        'Write-GitStatusPromptAsync',
+        'Convert-GitStatusOutput',
+        'Get-GitStatusBufferCells',
+        'Write-BufferCellsToPosition',
+
         'Write-Prompt',
         'Get-GitStatus', 
         'Enable-GitColors',