If you have repos in github that you'd like to port to gitlab, with all branches and tags, this will do it. If you want to port your wikis too, this will also work, although it's only a 90% solution for wikis. Github and gitlab use different file name and markdown conventions. Run the command port_repos_and_wikis_from_github_to_gitlab.sh to get …

convert_github_md_to_gitlab_format.sh

#!/bin/bash

echo
echo "Processing all *.md files in current directory..."
echo

# Loop through all .md files in directory and rename spaces to dashes
for file in *" "*; do
  echo "Renaming $file"
  mv -- "$file" "${file// /-}"
done

for file in *"("*; do
  echo "Renaming $file"
  mv -- "$file" "${file//(/}"
done

for file in *")"*; do
  echo "Renaming $file"
  mv -- "$file" "${file//)/}"
done

# Loop through all .md files in directory and convert them
for file in `find . -name '*.md'` ;
do
  echo "Converting ${file}";
  ruby ~/dotfiles/bin/github_wiki_to_gitlab_format.rb -i $file -o $file
done

echo "Complete."

github_wiki_to_gitlab_format.rb

#!/usr/bin/ruby

require 'optparse'

options = {}
optparse = OptionParser.new do |opts|
  opts.banner = "Usage: convert_github_wiki_links_to_gitlab_format.rb"
  opts.on("-i", "--input filepath", "Input file path (required)") do |i|
    options[:input] = i
  end
  opts.on("-o", "--output filepath", "Output file path (required)") do |i|
    options[:output] = i
  end
  opts.on('-h', '--help', 'Display this screen') do
    puts opts
    exit
  end
end

begin
  optparse.parse!
  mandatory = [:input, :output] # Enforce the presence of
  missing = mandatory.select { |param| options[param].nil? } # the -t and -f switches
  if not missing.empty? #
    puts "Missing options: #{missing.join(', ')}"
    puts optparse
    exit
  end
rescue OptionParser::InvalidOption, OptionParser::MissingArgument
  puts $!.to_s # Friendly output when parsing fails
  puts optparse
  exit
end

temp_file = "#{options[:output]}.tmp"
outfile = File.open(temp_file, 'w')

File.open(options[:input], 'r').each do |input_line|
  link_match = input_line.match(/(?<prelink>.*)\[\[(?<link>.+)\]\](?<postlink>.*)/)
  if (link_match)
    pretty_title = link_match[:link]
    corrected_link = pretty_title.gsub(" ", "-")
    corrected_link = corrected_link.gsub("(", "-")
    corrected_link = corrected_link.gsub(")", "-")
    output_line = "#{link_match[:prelink]}[#{pretty_title}](#{corrected_link})#{link_match[:postlink]}"
    outfile << output_line << "\n"
  else
    outfile << input_line
  end
end

outfile.close
File.rename(temp_file, options[:output])

port_repos_and_wikis_from_github_to_gitlab.sh

#!/bin/bash

if [ "$#" -lt 3 ]; then
    echo "Usage: $0 githubTeam gitlabTeam repoNameToPortA [repoNameToPortB] ... [repoNameToPortZ]"
    exit 1
fi
ORIG_TEAM=$1
DEST_TEAM=$2
shift
shift
repo_names_array=( "$@" )

echo
echo "This script ports the following repos and their wikis from:"
echo
for repo_name in "${repo_names_array[@]}"
do
  echo -e https://github.com/${ORIG_TEAM}/${repo_name}.git
done
for repo_name in "${repo_names_array[@]}"
do
  echo -e https://github.com/${ORIG_TEAM}/${repo_name}.wiki.git
done

echo
echo to these repos:
echo
for repo_name in "${repo_names_array[@]}"
do
  echo -e https://gitlab.com/${DEST_TEAM}/${repo_name}.git
done
for repo_name in "${repo_names_array[@]}"
do
  echo -e https://gitlab.com/${DEST_TEAM}/${repo_name}.wiki.git
done

echo
echo "The destination repos must already exist, but their wikis don't need to."
echo "This may take some time..."
read -p "Press [Enter] key to continue"
echo

# and now loop through the repo names:
for repo_name in "${repo_names_array[@]}"
do
  # Gitlab needs lowercase repo names, and dots turn into dashes
  gitlab_repo_name=`echo "print '$repo_name'.downcase.gsub('.', '-')" | ruby`

  git clone https://github.com/${ORIG_TEAM}/${repo_name}.git

  if cd ${repo_name}; then
#    git submodule update --init --recursive
    git remote add gitlab https://gitlab.com/${DEST_TEAM}/${gitlab_repo_name}.git
    git push gitlab refs/remotes/origin/*:refs/heads/*
    git push gitlab --tags
    cd ..
  else
    echo "Repo ${repo_name} could not be cloned. Aborting!"
    exit 1
  fi

  git clone https://github.com/${ORIG_TEAM}/${repo_name}.wiki.git
  if cd ${repo_name}.wiki; then
    git tag -a gitlab_wiki_conversion_before -m "Tag before conversion of github wiki links to gitlab format."
    convert_github_md_to_gitlab_format.sh
    git add . -A
    git commit -m "Automatically converted github wiki links to gitlab format."
    git tag -a gitlab_wiki_conversion_after -m "Tag after conversion of github wiki links to gitlab format."
    git remote add gitlab https://gitlab.com/${DEST_TEAM}/${gitlab_repo_name}.wiki.git
    git push gitlab master
    git push gitlab refs/remotes/origin/*:refs/heads/*
    git push gitlab --tags
    cd ..
  else
    echo "No wiki could be cloned. Continuing..."
  fi
done

echo Done!

Does it work the other way around?