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Git .gitattributes

Attributes describe per-path handling such as text normalization, diff behavior or filters. They are different from ignore rules.

How it works

The desk chooses LF-normalized text for Markdown and treats a fictional binary file as non-text. The lab checks the effective attributes for both paths. This tests the rule selection without pretending that a binary file becomes mergeable text. Before renormalizing an existing repository, inspect the staged diff and coordinate with collaborators.

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 gitattributes.ps1 in a separate empty learning folder and run it in a separate process: powershell -NoProfile -ExecutionPolicy Bypass -File .\gitattributes.ps1. The execution-policy option applies to that process, not your machine policy.

The script creates bhylu-git-gitattributes 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.

Download the complete gitattributes.ps1 lab

Example

gitattributes.ps1

# Bhylu Git lab: .gitattributes
# 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-gitattributes'
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
    Write-LabFile '.gitattributes' '*.md text eol=lf\n*.bin -text'
    git add '--' .gitattributes
    Assert-Equal (git check-attr text eol '--' notes.md) @('notes.md: text: set','notes.md: eol: lf')
    Assert-Equal (git check-attr text '--' diagram.bin) @('diagram.bin: text: unset')
    Write-Output 'Verified: gitattributes'
} finally { Pop-Location }
Focus on the lesson commands

This excerpt omits the seed repository and guard helpers. Use the complete download to run it.

Lesson excerpt

Write-LabFile '.gitattributes' '*.md text eol=lf\n*.bin -text'
git add '--' .gitattributes
Assert-Equal (git check-attr text eol '--' notes.md) @('notes.md: text: set','notes.md: eol: lf')
Assert-Equal (git check-attr text '--' diagram.bin) @('diagram.bin: text: unset')

Expected result

Markdown is treated as text with LF line endings; diagram.bin has text unset.

The complete script ends with Verified: gitattributes only after its checks pass. Object IDs, temporary paths and progress output can differ.

An eol policy controls checkout/check-in handling for matched text paths, while the exact behavior also depends on existing index content and configuration. Adding the file alone does not rewrite every historic blob. Keep binary and generated content policies explicit.

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