Bash
find . -type d -name .git -exec git --git-dir={} --work-tree=$PWD/{}/.. fetch -p \;
Powershell
Get-ChildItem -Recurse -Directory -Hidden -Filter .git | ForEach-Object { & git --git-dir="$($_.FullName)" --work-tree="$(Split-Path $_.FullName -Parent)" fetch -p }
git branch --merged | grep -v develop | xargs git branch -d
git branch --merged | %{$_.trim()} | ?{$_ -notmatch 'develop' -and $_ -notmatch 'master'} | %{ git branch -d $_ }