Cleanup_SquashCommits.ps1

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

$git = "git.exe"
$master = "master"
$protectedBranches = "$master|main"

# This script was adapted from ZSH script at 
# https://blog.takanabe.tokyo/en/2020/04/remove-squash-merged-local-git-branches/
# It is supplemented with code to track and pull all remote branches, to make sure all 
# remote branches ready for deletion are accounted for 
# It outputs the commands needed to delete the remote branches matching the ones it
# deletes locally.

function track_all_remote_branches() {
    $localBranches = &$git branch -l | Foreach-Object { $_.Trim() }
    &$git branch -r |
    Foreach-Object { $_.Trim() } |
    Where-Object { -not ($_ -match '\->') } | 
    Where-Object { -not ($_ -match "(^\*|$protectedBranches)") } | 
    ForEach-Object {
        $local = $_ -Replace 'origin/', ''
        if ($localBranches.Contains($local)) {
            Write-Host "Already tracking $_"
        }
        else {
            Write-Host "Tracking $_"
            &$git branch --track "$local" "$_"
                    
        }
    } 
    &$git fetch --all
    &$git pull --all
}

function git_prune_remote() {
    Write-Host "Start removing out-dated remote merged branches"
    &$git fetch --prune | Out-Null
    Write-Host "Finish removing out-dated remote merged branches"
}

function git_remove_merged_local_branch() {
    Write-Host "Start removing out-dated local merged branches"
    $mergedLocalBranches = &$git branch --merged | Where-Object { -not ($_ -match "(^\*|$protectedBranches)") }
    $deletedBranches = New-Object System.Collections.Generic.List[string]
    foreach ($branch in $mergedLocalBranches) {
        $branch = $branch.Trim()
        $deletedBranches.Add($branch)
        Write-Host "Removing $branch locally"
        &$git branch -D $branch | Out-Null
    }
    Write-Host "Finish removing out-dated local merged branches"
    return $deletedBranches
}

# When we use `Squash and merge` on GitHub,
# `&$git branch --merged` cannot detect the squash-merged branches.
# As a result, git_remove_merged_local_branch() cannot clean up
# unused local branches. This function detects and removes local branches
# when remote branches are squash-merged.
#
# There is an edge case. If you add suggested commits on GitHub,
# the contents in local and remote are different. As a result,
# This clean up function cannot remove local squash-merged branch.
function git_remove_squash_merged_local_branch() {
    Write-Host "Start removing out-dated local squash-merged branches"
    &$git checkout -q $master

    $branches = &$git for-each-ref refs/heads/ "--format=%(refname:short)" 
    $deletedBranches = New-Object System.Collections.Generic.List[string]
    foreach ($branch in $branches) {
        #Write-Host $branch
        $ancestor = $(&$git merge-base $master $branch) 
        #Write-Host "A: $ancestor"
        $rp = &$git rev-parse "$branch^{tree}"
        #Write-Host "RP: $rp"
        $ct = &$git commit-tree "$rp" -p $ancestor -m _
        #Write-Host "CT: $ct"
        $cherry = &$git cherry $master "$ct"  
        #Write-Host "Cherry: $cherry"
        if ($cherry -match "\-.*") {
            Write-Host "Removing $branch locally"
            &$git branch -D $branch | Out-Null
            $deletedBranches.Add($branch)
        }
    }
    Write-Host "Finish removing out-dated local squash-merged branches"
    return $deletedBranches
}

# Clean up remote and local branches
track_all_remote_branches
git_prune_remote
$mergedBranches = git_remove_merged_local_branch
$squashMergedBranches = git_remove_squash_merged_local_branch


Write-Host "Script to delete remote branches"
foreach ($b in ($mergedBranches + $squashMergedBranches | Select-Object -uniq)) {
    Write-Output "git push origin --delete $b"
}