Use-Git.ps1

function Use-Git
{
    <#
    .SYNOPSIS
        Use Git
    .DESCRIPTION
        Calls the git application, with whatever arguments are provided.

        Arguments can be provided with -GitArgument, which will automatically be bound to all parameters provided without a name.

        Input can also be piped in.
        
        If the input is a directory, Use-Git will Push-Location that directory.
        Otherwise, it will be passed as a positional argument (after any other arguments).

        Use-Git will combine errors and output, so that git output to standard error is handled without difficulty.
    .NOTES
        For almost everything git does, calling Use-Git is the same as calling git directly.

        If you have any difficulties passing parameters to git, try enclosing them in quotes.
    .LINK
        Out-Git
    .Example
        # Log entries are returned as objects, with properties and methods.
        git log -n 1 | Get-Member
    .Example
        # Status entries are converted into objects.
        git status
    .Example
        # Display untracked files.
        git status | Select-Object -ExpandProperty Untracked
    .Example
        # Display the list of branches, as objects.
        git branch
    .NOTES
        Use-Git will generate two events before git runs. They will have the source identifiers of "Use-Git" and "Use-Git $GitArgument"
    #>

    [Alias('git')]
    [CmdletBinding(PositionalBinding=$false,SupportsShouldProcess,ConfirmImpact='Low')]
    param(
    # Any arguments passed to git. All positional arguments will automatically be passed to -GitArgument.
    [Parameter(ValueFromRemainingArguments)]
    [Alias('GitArguments')]
    [string[]]
    $GitArgument,

    # An optional input object.
    # If the Input is a directory, Use-Git will Push-Location to that directory
    # Otherwise, it will be passed as a postional argument (after any other arguments)
    [Parameter(ValueFromPipeline)]
    [PSObject[]]
    $InputObject
    )

    begin {
        if (-not $script:CachedGitCmd) { # If we haven't cahced the git command
            # go get it.
            $script:CachedGitCmd = $ExecutionContext.SessionState.InvokeCommand.GetCommand('git', 'Application')
        }
        if (-not $script:CachedGitCmd) { # If we still don't have git
            throw "Git not found"        # throw.
        }
        if (-not $script:RepoRoots) {    # If we have not yet created a cache of repo roots
            $script:RepoRoots = @{}      # do so now.
        }

        $myInv = $MyInvocation
        $callstackPeek = @(Get-PSCallStack)[1]
        $callingContext =
            if ($callstackPeek.InvocationInfo.MyCommand.ScriptBlock) {
                @($callstackPeek.InvocationInfo.MyCommand.ScriptBlock.Ast.FindAll({
                    param($ast) 
                        $ast.Extent.StartLineNumber -eq $myInv.ScriptLineNumber -and
                        $ast.Extent.StartColumnNumber -eq $myInv.OffsetInLine -and 
                        $ast -is [Management.Automation.Language.CommandAst]
                },$true))[0]
            }
        
        $argumentNumber = 0
        foreach ($commandElement in $callingContext.CommandElements) {
            if ($commandElement.parameterName -in 'd', 'v') {
                # If they passed -d/-D or -v/-V, they probably don't mean -Debug/-Verbose
                $beforeArgs = @(if ($argumentNumber) { $GitArgument[0..$argumentNumber]})
                $afterArgs  = @(if ($argumentNumber + 1 -le $gitArgument.Length) {
                    $GitArgument[($argumentNumber + 1)..($GitArgument.Length - 1)]
                })
                $GitArgument = @($beforeArgs) + @("$($commandElement.Extent)") + @($afterArgs)
                if ($commandElement.parameterName -eq 'd') { # Also, if they passed -d/-D, they probably don't want to be confirmed
                    $ConfirmPreference ='none' # so set confirm impact to none
                }
            }
            $argumentNumber++
        }

        $progId = Get-Random
        $dirCount = 0
        $RepoNotRequired = 'clone','init','version','help'  # A small number of git operations do not require a repo. List them here.
    }
    process {
        # First, we need to take any input and figure out what directories we are going into.
        $directories = @()
        $inputObject = 
            @(foreach ($in in $inputObject) {
                if ($in -is [IO.FileInfo]) { # If the input is a file
                    $in.Fullname             # return the full name of that file.
                } elseif ($in -is [IO.DirectoryInfo]) {
                    $directories += Get-Item -LiteralPath $in.Fullname # If the input was a directory, keep track of it.
                } else {
                    # Otherwise, see if it was a path and it was a directory
                    if ((Test-Path $in -ErrorAction SilentlyContinue) -and 
                        (Get-Item $in -ErrorAction SilentlyContinue) -is [IO.DirectoryInfo]) {
                        $directories += Get-Item $in
                    } else {
                        $in
                    }
                }
            })

        # git sometimes like to return information along standard error, and CI/CD and user defaults sometimes set $ErrorActionPreference to 'Stop'
        # So we change $ErrorActionPreference before we call git, just in case.
        $ErrorActionPreference = 'continue'

        # Before we process each directory, make a copy of the bound parameters.
        $paramCopy = ([Ordered]@{} + $PSBoundParameters)

        
        # Now, we will force there to be at least one directory (the current path).
        # This makes the code simpler, because we are always going thru a loop.
        if (-not $directories) {
            $directories = @($pwd)
        } else {
            # It also gives us a change to normalize the directories into their full paths.
            $directories = @(foreach ($dir in $directories) { $dir.Fullname }) 
        }


        # For each directory we know of, we
        foreach ($dir in $directories) {
            $AllGitArgs = @(@($GitArgument) + $InputObject) # collect the combined arguments
            $OutGitParams = @{GitArgument=$AllGitArgs}      # and prepare a splat (to save precious space when reporting errors).
            $dirCount++
            if ($WhatIfPreference) {
                @{} + $PSBoundParameters
                continue
            }

            Push-Location -LiteralPath $dir                 # Then we Push into that directory.
            if (-not $script:RepoRoots[$dir]) {             # and see if we have a repo root
                $script:RepoRoots[$dir] = 
                    @("$(& $script:CachedGitCmd rev-parse --show-toplevel *>&1)") -like "*/*" -replace '/', [io.path]::DirectorySeparatorChar
                if (-not $script:RepoRoots[$dir] -and      # If we did not have a repo root
                    -not ($gitArgument -match "(?>$($RepoNotRequired -join '|'))") # and we are not doing an operation that does not require one
                ) {
                    Write-Warning "'$($dir)' is not a git repository" # warn that there is no repo (#21)
                    Pop-Location # pop back out of the directory
                    continue # and continue to the next one.
                }
            }
                        
            $OutGitParams.GitRoot = "$($script:RepoRoots[$dir])"
            Write-Verbose "Calling git with $AllGitArgs"
            if ($dirCount -gt 1) {                
                Write-Progress -PercentComplete (($dirCount * 5) % 100) -Status "git $allGitArgs " -Activity "$($dir) " -Id $progId
            }
        
            if (($ConfirmPreference -eq 'None' -and -not $paramCopy.Confirm) -or # If we have indicated we do not care about -Confirmation, don't prompt
                $PSCmdlet.ShouldProcess("$pwd : git $allGitArgs") # otherwise, as for confirmation to run.
            ) {
                $eventSourceIds = @("Use-Git","Use-Git $allGitArgs")
                $messageData = @{
                    GitRoot = "$pwd"
                    GitCommand = @(@("git") + $AllGitArgs) -join ' '
                }
                $null =
                    foreach ($sourceIdentifier in $eventSourceIds) {
                        New-Event -SourceIdentifier $sourceIdentifier -MessageData $messageData
                    }
                & $script:CachedGitCmd @AllGitArgs *>&1       | # Then we run git, combining all streams into output.
                                                                # then pipe to Out-Git, which will
                    Out-Git @OutGitParams # output git as objects.
                                        
                    # These objects are decorated for the PowerShell Extended Type System.
                    # This makes them easy to extend and customize their display.
                    # If Out-Git finds one or more extensions to run, these can parse the output.
            }
            Pop-Location # After we have run, Pop back out of the location.
        }        
    }

    end {
        if ($dirCount -gt 1) {
            Write-Progress -completed -Status "$allGitArgs " -Activity " " -Id $progId
        }
    }
}