Linux

parse_git_branch() {
	git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/(\1)/'
}

export PS1='\[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[01;31m\]$(parse_git_branch)\[\033[00m\]\$ '

Windows

function Write-BranchName () {
    try {
        $branch = git rev-parse --abbrev-ref HEAD

        if ($branch -eq "HEAD") {
            # we're probably in detached HEAD state, so print the SHA
            $branch = git rev-parse --short HEAD
            Write-Host "($branch)" -NoNewline -ForegroundColor "red"
        }
        else {
            # we're on an actual branch, so print it
            Write-Host "($branch)" -NoNewline -ForegroundColor "blue"
        }
    } catch {
        # we'll end up here if we're in a newly initiated git repo
        Write-Host "(no branches yet)" -NoNewline -ForegroundColor "yellow"
    }
}

function prompt {
    $base = "PS "
    $path = "$($executionContext.SessionState.Path.CurrentLocation)"
    $userPrompt = "$('>' * ($nestedPromptLevel + 1)) "

    Write-Host "`n$base" -NoNewline

    #if (Test-Path .git) {
    #    Write-Host $path -NoNewline -ForegroundColor "green"
    #    Write-BranchName
    #}
    #else {
    #    # we're not in a repo so don't bother displaying branch name/sha
    #    Write-Host $path -NoNewline -ForegroundColor "green"
    #}
    Write-Host $path -NoNewline -ForegroundColor "green"
    Write-BranchName

    return $userPrompt
}