powershell profile incorporating git status

Microsoft.PowerShell_profile.ps1

#! /usr/bin/env pwsh

function Prompt {

    $promptColor, 
    $infoColor, 
    $warnColor, 
    $errorColor, 
    $defaultColor = 
    'Cyan', 
    'Green', 
    'Yellow', 
    'Red', 
    'White'

    $version = $PSVersionTable.PSVersion.ToString()

    # Substitute shortened form of $HOME if present 
    # We must double-up Windows path-separator characters '\' (backslash) before passing off for regex evaluation.
    # Regex library is C-based and '\' (backslash) is the special-quoted-character-prefix. A literal backslash is represented as '\\' 
    $myHome = if ($IsLinux -or $IsMacOS) { $HOME } else {$HOME -replace '\\', '\\' }
    $location = (Get-Location).Path -replace $myHome, '~' 

    Write-Host "PS v$version $location " -NoNewline -ForegroundColor $promptColor

    # Get details about current repository
    # We can't append "--abrev-ref HEAD" as it gets interpreted as additional arguments to "--short"
    $gitDir, 
    $insideGitDir, 
    $isBareRepo, 
    $insideWorkTree, 
    $localRev, 
    $shortSha = 
    (& git rev-parse `
            --git-dir `
            --is-inside-git-dir `
            --is-bare-repository `
            --is-inside-work-tree `
            '@' `
            --short HEAD 2> $null)

    # Are we in a git repository?
    # $gitDir is relative path to '.git' dir for local repository, empty for non-repository
    if ($gitDir) {

        # Separator before git info
        Write-Host '| ' -NoNewline -ForegroundColor $promptColor

        function Test-DetachedHead { 
            $head = Get-Content "$gitDir\HEAD"
            -not ($head -match 'ref: ')
        }
  
        # Initialise local vars
        $fgColor, $next, $local, $remote, $status = $infoColor, @(), @(), @(), @()

        ## Process local repo 'dirty' status...

        # Check for staged changes
        $staged = [bool](& git diff --no-ext-diff --staged)
        # Check for unstaged changes
        $unstaged = [bool](& git diff --no-ext-diff)
        # Required actions to migrate workspace state to local repository
        if ($unstaged) { $next += , 'add' } 
        if ($staged) { $next += , 'commit' } 
        if ($next) { $fgColor = $warnColor }

        ## Process 'local' repo status...

        if (Test-DetachedHead) {
            $local = "local:$shortSha (detached)"
            # Add any tags for current revision...
            if ($localTags = (&git tag --points-at '@')) { 
                $local += " tags:$localTags" 
            }            
            $fgColor = $errorColor
        }
        else {
            $localBranch = $(& git symbolic-ref --short HEAD)
            $local = "local:$localBranch"
        }

        ## Process 'remote' repo status...
        
        # Remote status is irrelevant for detached local repo
        if (-not (Test-DetachedHead)) {
            $remoteBranch = (& git rev-parse --abbrev-ref '@{u}')
            $remote = "remote:$remoteBranch"
            # NOTE: Relies on a recent 'git fetch' operation for fresh remote information
            $remoteRev = (& git rev-parse '@{u}')
            $lastCommonRev = (& git merge-base '@' '@{u}')
            # Check for valid values
            if (($remoteRev -ne '@u') -and $lastCommonRev) {
                # NOTE: We are not modifying $fgColor for remote state
                if ($localRev -eq $remoteRev) {
                    # Local and remote repo committed revisions match.
                }
                elseif ($localRev -eq $lastCommonRev) {
                    # Remote repo ahead. Pull required.
                    # NOTE: Leading (,) below converts RHS to an array 
                    # -  and stops conversion of $next to scalar string 
                    $next += , 'pull'
                }
                elseif ($remoteRev -eq $lastCommonRev) {
                    # Local repo ahead. Push required.
                    $next += , 'push'
                }
                else {
                    # Local and origin repos have diverged - pull then push. 
                    $next += 'pull', 'push'
                }
            }
        }

        ## Build displayed 'status'...
        
        if ($next) { $status += "next:$($next -join ',')" }
        if ($local) { $status += $local }  # $local will always have content
        if ($remote) { $status += $remote }
        Write-Host "git $status" -NoNewline -ForegroundColor $fgColor 
    }

    Write-Host "`n`$" -NoNewline -ForegroundColor $defaultColor
    return " "
}