Add the Remove-PoshGitFromProfile function

This is needed to be able to install/uninstall Posh-Git via Git for
Windows' installer/uninstaller.

See git-for-windows/build-extra#401 for details.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

src/Utils.ps1

@@ -216,6 +216,123 @@ function Add-PoshGitToProfile {
     }
 }
 
+<#
+.SYNOPSIS
+    Modifies your PowerShell profile (startup) script so that it does not import
+    the posh-git module when PowerShell starts.
+.DESCRIPTION
+    Checks if your PowerShell profile script is importing posh-git and if it does,
+    removes the command to import the posh-git module. This will cause PowerShell
+    to no longer load posh-git whenever PowerShell starts.
+.PARAMETER AllHosts
+    By default, this command modifies the CurrentUserCurrentHost profile
+    script.  By specifying the AllHosts switch, the command updates the
+    CurrentUserAllHosts profile (or AllUsersAllHosts, given -AllUsers).
+.PARAMETER AllUsers
+    By default, this command modifies the CurrentUserCurrentHost profile
+    script.  By specifying the AllUsers switch, the command updates the
+    AllUsersCurrentHost profile (or AllUsersAllHosts, given -AllHosts).
+    Requires elevated permissions.
+.EXAMPLE
+    PS C:\> Remove-PoshGitFromProfile
+    Updates your profile script for the current PowerShell host to stop importing
+    the posh-git module when the current PowerShell host starts.
+.EXAMPLE
+    PS C:\> Remove-PoshGitFromProfile -AllHosts
+    Updates your profile script for all PowerShell hosts to no longer import the
+    posh-git module whenever any PowerShell host starts.
+.INPUTS
+    None.
+.OUTPUTS
+    None.
+#>
+function Remove-PoshGitFromProfile {
+    [CmdletBinding(SupportsShouldProcess)]
+    param(
+        [Parameter()]
+        [switch]
+        $AllHosts,
+
+        [Parameter()]
+        [switch]
+        $AllUsers,
+
+        [Parameter(ValueFromRemainingArguments)]
+        [psobject[]]
+        $TestParams
+    )
+
+    if ($AllUsers -and !(Test-Administrator)) {
+        throw 'Removing posh-git from an AllUsers profile requires an elevated host.'
+    }
+
+    $underTest = $false
+
+    $profileName = $(if ($AllUsers) { 'AllUsers' } else { 'CurrentUser' }) `
+                 + $(if ($AllHosts) { 'AllHosts' } else { 'CurrentHost' })
+    Write-Verbose "`$profileName = '$profileName'"
+
+    $profilePath = $PROFILE.$profileName
+    Write-Verbose "`$profilePath = '$profilePath'"
+
+    # Under test, we override some variables using $args as a backdoor.
+    if (($TestParams.Count -gt 0) -and ($TestParams[0] -is [string])) {
+        $profilePath = [string]$TestParams[0]
+        $underTest = $true
+        if ($TestParams.Count -gt 1) {
+            $ModuleBasePath = [string]$TestParams[1]
+        }
+    }
+
+    if (!$profilePath) { $profilePath = $PROFILE }
+
+    if (!$profilePath) {
+        Write-Warning "Skipping add of posh-git import to profile; no profile found."
+        Write-Verbose "`$PROFILE              = '$PROFILE'"
+        Write-Verbose "CurrentUserCurrentHost = '$($PROFILE.CurrentUserCurrentHost)'"
+        Write-Verbose "CurrentUserAllHosts    = '$($PROFILE.CurrentUserAllHosts)'"
+        Write-Verbose "AllUsersCurrentHost    = '$($PROFILE.AllUsersCurrentHost)'"
+        Write-Verbose "AllUsersAllHosts       = '$($PROFILE.AllUsersAllHosts)'"
+        return
+    }
+
+    if (Test-Path -LiteralPath $profilePath) {
+        # If the profile script exists and is signed, then we should not modify it
+        if (!(Get-Command Get-AuthenticodeSignature -ErrorAction SilentlyContinue))
+        {
+            Write-Verbose "Platform doesn't support script signing, skipping test for signed profile."
+        }
+        else {
+            $sig = Get-AuthenticodeSignature $profilePath
+            if ($null -ne $sig.SignerCertificate) {
+                Write-Warning "Skipping add of posh-git import to profile; '$profilePath' appears to be signed."
+                Write-Warning "Add the command 'Import-Module posh-git' to your profile and resign it."
+                return
+            }
+        }
+
+        $oldProfile = @(Get-Content $profilePath)
+
+        . $currentVersionPath\src\Utils.ps1
+        $oldProfileEncoding = Get-FileEncoding $profilePath
+
+        $newProfile = @()
+        foreach($line in $oldProfile) {
+            if ($line -like '*PoshGitPrompt*') { continue; }
+            if ($line -like '*Load posh-git example profile*') { continue; }
+
+            if($line -like '. *posh-git*profile.example.ps1*') {
+                continue;
+            }
+            if($line -like 'Import-Module *\src\posh-git.psd1*') {
+                continue;
+            }
+            $newProfile += $line
+        }
+        Set-Content -path $profilePath -value $newProfile -Force -Encoding $oldProfileEncoding
+    }
+}
+
 <#
 .SYNOPSIS
     Gets the file encoding of the specified file.

src/posh-git.psd1

@@ -33,6 +33,7 @@ FunctionsToExport = @(
     'Get-PromptPath',
     'New-GitPromptSettings',
     'Remove-GitBranch',
+    'Remove-PoshGitFromProfile',
     'Update-AllBranches',
     'Write-GitStatus',
     'Write-GitBranchName',

src/posh-git.psm1

@@ -171,6 +171,7 @@ $exportModuleMemberParams = @{
         'Get-PromptPath',
         'New-GitPromptSettings',
         'Remove-GitBranch',
+        'Remove-PoshGitFromProfile',
         'Update-AllBranches',
         'Write-GitStatus',
         'Write-GitBranchName',

test/Utils.Tests.ps1

@@ -101,6 +101,26 @@ New-Alias pscore C:\Users\Keith\GitHub\rkeithhill\PowerShell\src\powershell-win-
             $expectedContent += "${newLine}${newLine}Import-Module '$(Join-Path $moduleBasePath posh-git).psd1'"
             $content -join $newLine | Should -BeExactly $expectedContent
         }
+        It 'Removes import from the profile correctly' {
+            $profileContentPSCX = @'
+Import-Module PSCX
+'@
+            $profileContentPoshGit = @'
+Import-Module posh-git
+'@
+            $profileContent = $profileContentPSCX + $profileContentPoshGit
+            Set-Content $profilePath -Value $profileContent -Encoding Ascii
+
+            $output = Remove-PoshGitFromProfile $profilePath 3>&1
+
+            Write-Host "output: $output"
+            $output[1] | Should -Match 'posh-git appears'
+            Get-FileEncoding $profilePath | Should -Be 'ascii'
+            $content = Get-Content $profilePath
+            $content.Count | Should -Be 1
+            $expectedContent = Convert-NativeLineEnding $profileContentPSCX
+            $content -join $newline | Should -BeExactly $expectedContent
+        }
     }
 
     Context 'Get-PromptConnectionInfo' {