Delete old git branch by specifying the date

deleteOldBranch.ps1

param(
  [Parameter(Mandatory = $false)]
  [string] $Remote = "origin",

  # Cutoff in ISO format, e.g. 2025-01-01
  [Parameter(Mandatory = $true)]
  [datetime] $CutoffDate,

  # Never delete these exact branch names
  [string[]] $ProtectBranches = @("main", "master", "develop"),

  # Never delete branches matching these wildcards (PowerShell -like)
  [string[]] $ProtectPatterns = @("release/*", "hotfix/*"),

  # If set, prints what would be deleted but does not delete
  [switch] $WhatIf
)

Set-StrictMode -Version Latest
$ErrorActionPreference = "Stop"

function Run-Git([string[]]$Args) {
  $out = & git @Args 2>&1
  if ($LASTEXITCODE -ne 0) { throw "git $($Args -join ' ') failed:`n$out" }
  return $out
}

# Ensure we're in a git repo
Run-Git @("rev-parse", "--is-inside-work-tree") | Out-Null

Write-Host "Fetching latest refs from '$Remote'..."
Run-Git @("fetch", "--prune", $Remote) | Out-Null

# Protect default branch (origin/HEAD -> origin/<default>)
$defaultBranch = $null
try {
  $sym = Run-Git @("symbolic-ref", "--quiet", "refs/remotes/$Remote/HEAD")
  # refs/remotes/origin/main -> main
  $defaultBranch = ($sym.Trim() -replace "^refs/remotes/$Remote/", "")
} catch {
  # ignore if not set
}
if ($defaultBranch) {
  if ($ProtectBranches -notcontains $defaultBranch) { $ProtectBranches += $defaultBranch }
  Write-Host "Detected default branch: $defaultBranch (protected)"
}

$cutoffUtc = $CutoffDate.ToUniversalTime()

# List remote branches + unix commit time
# Output format: origin/feature/foo<TAB>1700000000
$lines = Run-Git @("for-each-ref", "--format=%(refname:short)`t%(committerdate:unix)", "refs/remotes/$Remote")

$candidates = @()

foreach ($line in ($lines -split "`r?`n")) {
  if ([string]::IsNullOrWhiteSpace($line)) { continue }

  $parts = $line -split "`t"
  if ($parts.Count -lt 2) { continue }

  $ref = $parts[0].Trim()         # origin/branch
  $unix = [int64]$parts[1].Trim() # seconds

  if (-not $ref.StartsWith("$Remote/")) { continue }

  $branch = $ref.Substring($Remote.Length + 1) # remove "origin/"
  if ($branch -eq "HEAD") { continue }

  if ($ProtectBranches -contains $branch) { continue }

  $isProtectedByPattern = $false
  foreach ($pat in $ProtectPatterns) {
    if ($branch -like $pat) { $isProtectedByPattern = $true; break }
  }
  if ($isProtectedByPattern) { continue }

  $commitUtc = [DateTimeOffset]::FromUnixTimeSeconds($unix).UtcDateTime
  if ($commitUtc -lt $cutoffUtc) {
    $candidates += [pscustomobject]@{
      Branch    = $branch
      CommitUtc = $commitUtc
    }
  }
}

$candidates = $candidates | Sort-Object CommitUtc

if ($candidates.Count -eq 0) {
  Write-Host "No branches older than $($cutoffUtc.ToString("u")) to delete."
  exit 0
}

Write-Host "Branches to delete (tip commit older than $($cutoffUtc.ToString("u"))):"
$candidates | ForEach-Object { Write-Host (" - {0} (last commit {1:u})" -f $_.Branch, $_.CommitUtc) }

if ($WhatIf) {
  Write-Host "`nWhatIf set; no deletions performed."
  exit 0
}

Write-Host "`nDeleting branches on remote '$Remote'..."
foreach ($b in $candidates.Branch) {
  try {
    Run-Git @("push", $Remote, "--delete", $b) | Out-Null
    Write-Host "Deleted: $b"
  } catch {
    Write-Warning "Failed to delete '$b': $($_.Exception.Message)"
  }
}

Usage

Dry Run

.\Delete-OldBranches.ps1 -CutoffDate "2025-01-01" -WhatIf

Actual Delete

.\Delete-OldBranches.ps1 -CutoffDate "2025-01-01"

Protect extra patterns:

.\Delete-OldBranches.ps1 -CutoffDate "2025-01-01" -ProtectPatterns @("release/*","hotfix/*","keep/*") -WhatIf