Git Worktrees
A linked worktree gives another branch its own working directory while sharing the repository’s object storage. It is useful for reviewing or testing two branches side by side.
How it works
The second desk folder checks out a new inspection branch. It shares committed history with the original repository but has a separate index and working files. We change and commit a note there, then verify that the main working tree is unchanged. Git normally prevents checking out the same branch in multiple worktrees at once.
Run the disposable lab
Use Windows PowerShell 5.1 or later and Git 2.28 or later. The reviewed CLI is Git for Windows 2.53.0.windows.2. These are PowerShell examples, not Git Bash commands. Save the download as worktrees.ps1 in a separate empty learning folder and run it in a separate process: powershell -NoProfile -ExecutionPolicy Bypass -File .\worktrees.ps1. The execution-policy option applies to that process, not your machine policy.
The script creates bhylu-git-worktrees and refuses an existing folder. It supplies two fictional seed files and repository-local settings, then runs the lesson commands. The literal separator is quoted as '--' so PowerShell passes it through the guard. A guard function named git calls the real CLI and stops on unexpected failures; Expect-GitFailure checks deliberately refused operations. Child-process configuration isolates your personal Git settings. File transports are allowed only for owned local remotes; internet transports are disabled in this lab. No hosting account, Apache or MySQL service is required. There is no Git playground. Leave the generated folder for inspection; choose another empty parent to run again.
Example
# Bhylu Git lab: Worktrees
# Run in a separate PowerShell process, in an empty learning folder.
# Existing lab folders are refused; nothing is pushed to an internet host.
$ErrorActionPreference = 'Stop'
$script:GitExe = (Get-Command git -CommandType Application | Select-Object -First 1).Source
$script:LabRoot = Join-Path (Get-Location) 'bhylu-git-worktrees'
if (Test-Path -LiteralPath $script:LabRoot) { throw 'Lab folder already exists. Choose another empty parent folder.' }
New-Item -ItemType Directory -Path $script:LabRoot | Out-Null
$env:GIT_CONFIG_NOSYSTEM = '1'
$env:GIT_CONFIG_GLOBAL = Join-Path $script:LabRoot 'empty-global-config'
[IO.File]::WriteAllText($env:GIT_CONFIG_GLOBAL, '')
$env:GIT_TERMINAL_PROMPT = '0'
$env:GIT_EDITOR = 'true'
$env:GIT_SEQUENCE_EDITOR = 'true'
$env:GIT_AUTHOR_DATE = '2026-01-10T10:00:00+00:00'
$env:GIT_COMMITTER_DATE = $env:GIT_AUTHOR_DATE
function git {
& $script:GitExe -c protocol.allow=never -c protocol.file.allow=always @args
if ($LASTEXITCODE -ne 0) { throw "Git exited with code $LASTEXITCODE" }
}
function Expect-GitFailure {
& $script:GitExe -c protocol.allow=never -c protocol.file.allow=always @args
if ($LASTEXITCODE -eq 0) { throw 'Expected Git to refuse this operation' }
}
function Assert-Equal($Actual, $Expected) {
if ((($Actual | Out-String).Trim()) -cne (($Expected | Out-String).Trim())) { throw "Expected [$Expected], got [$Actual]" }
}
function Write-LabFile([string]$Name, [string]$Text) {
$target = [IO.Path]::GetFullPath((Join-Path (Get-Location) $Name))
if (!$target.StartsWith($script:LabRoot + [IO.Path]::DirectorySeparatorChar, [StringComparison]::OrdinalIgnoreCase)) { throw 'Path outside lab' }
[IO.Directory]::CreateDirectory([IO.Path]::GetDirectoryName($target)) | Out-Null
[IO.File]::WriteAllText($target, ($Text.Replace('\n', "`n") + "`n"), (New-Object Text.UTF8Encoding($false)))
}
function New-LabRepo([string]$Name) {
New-Item -ItemType Directory -Path $Name | Out-Null
Push-Location $Name
try {
git init --initial-branch=main
git config --local user.name 'Repair Lab'
git config --local user.email 'repair@example.invalid'
git config --local core.autocrlf false
git config --local commit.gpgSign false
git config --local tag.gpgSign false
git config --local core.hooksPath (Join-Path $script:LabRoot 'empty-hooks')
Write-LabFile 'notes.md' 'Inspect hinge'
Write-LabFile 'tasks.txt' 'desk=open'
git add '--' notes.md tasks.txt
git commit -m 'Record initial repair plan'
} finally { Pop-Location }
}
Push-Location $script:LabRoot
try {
New-LabRepo 'desk'
Set-Location desk
git worktree add -b inspection ../inspection
git -C ../inspection config user.name 'Repair Lab'
Push-Location ../inspection
try {
Write-LabFile 'notes.md' 'Worktree inspection'
git add '--' 'notes.md'
git commit -m 'Inspect in second worktree'
} finally { Pop-Location }
Assert-Equal (Get-Content notes.md) @('Inspect hinge')
Assert-Equal (git show inspection:notes.md) @('Worktree inspection')
git worktree list
Write-Output 'Verified: worktrees'
} finally { Pop-Location }
Focus on the lesson commands
This excerpt omits the seed repository and guard helpers. Use the complete download to run it.
git worktree add -b inspection ../inspection
git -C ../inspection config user.name 'Repair Lab'
Push-Location ../inspection
try {
Write-LabFile 'notes.md' 'Worktree inspection'
git add '--' 'notes.md'
git commit -m 'Inspect in second worktree'
} finally { Pop-Location }
Assert-Equal (Get-Content notes.md) @('Inspect hinge')
Assert-Equal (git show inspection:notes.md) @('Worktree inspection')
git worktree list
Expected result
The original file retains Inspect hinge; the inspection branch records Worktree inspection in a second working directory.
The complete script ends with Verified: worktrees only after its checks pass. Object IDs, temporary paths and progress output can differ.
Shared objects do not mean shared uncommitted files. Remove finished linked worktrees through git worktree remove after checking their state instead of deleting metadata by hand. This teaching script leaves its owned folders for inspection.