How to migrate from Mercurial to Git

# Install git-remote-hg
# On macOS
brew install git-remote-hg

# On Ubuntu
sudo apt-get install git-remote-hg

# Clone Mercurial repository as Git
git clone hg::https://bitbucket.org/user/hg-repo git-repo

cd git-repo

# Add Git remote
git remote add origin https://github.com/user/new-repo.git

# Push to Git
git push -u origin main

# Install hg-fast-export
git clone https://github.com/frej/fast-export.git
cd fast-export

# Create empty Git repository
mkdir ../git-repo
cd ../git-repo
git init

# Import from Mercurial
../fast-export/hg-fast-export.sh -r /path/to/hg-repo

# Verify import
git log --oneline
git branch -a
git tag -l

# Add remote and push
git remote add origin https://github.com/user/repo.git
git push -u origin main
git push --all
git push --tags

# Create authors.txt
# Format: hgauthor=Git Author <[email protected]>

cat > authors.txt <<EOF
john=John Doe <[email protected]>
jane=Jane Smith <[email protected]>
bob=Bob Johnson <[email protected]>
EOF

# Use with hg-fast-export
hg-fast-export.sh -r /path/to/hg-repo -A authors.txt

# Extract all Mercurial authors
cd /path/to/hg-repo
hg log --template '{author}\n' | sort -u > ../hg-authors.txt

# Create mapping template
while read author; do
  # Try to extract email if present
  if [[ $author == *"<"* ]]; then
    echo "$author=$author"
  else
    echo "$author=$author <$author@example.com>"
  fi
done < ../hg-authors.txt > ../authors.txt

# Edit authors.txt to add proper names and emails

#!/bin/bash
# migrate-hg-to-git.sh

HG_REPO="/path/to/hg-repo"
GIT_REPO="/path/to/git-repo"
GIT_REMOTE="https://github.com/user/repo.git"
AUTHORS_FILE="authors.txt"
FAST_EXPORT="/path/to/fast-export"

echo "Starting Mercurial to Git migration..."

# 1. Generate authors file if doesn't exist
if [ ! -f "$AUTHORS_FILE" ]; then
  echo "Generating authors file..."
  cd "$HG_REPO"
  hg log --template '{author}\n' | sort -u | while read author; do
    echo "$author=$author <${author}@example.com>"
  done > "$AUTHORS_FILE"
  echo "Edit $AUTHORS_FILE with correct names and emails, then re-run"
  exit 1
fi

# 2. Create empty Git repository
echo "Creating Git repository..."
mkdir -p "$GIT_REPO"
cd "$GIT_REPO"
git init

# 3. Import from Mercurial
echo "Importing from Mercurial..."
"$FAST_EXPORT/hg-fast-export.sh" -r "$HG_REPO" -A "$AUTHORS_FILE"

# 4. Clean up Mercurial tags
echo "Converting tags..."
git for-each-ref refs/tags | while read sha type ref; do
  tag=${ref#refs/tags/}
  # Remove Mercurial default tag
  if [ "$tag" = "tip" ]; then
    git tag -d tip
  fi
done

# 5. Verify branches
echo "Branches:"
git branch -a

# 6. Verify tags
echo "Tags:"
git tag -l

# 7. Add remote
echo "Adding remote..."
git remote add origin "$GIT_REMOTE"

# 8. Push to Git
echo "Pushing to Git repository..."
git push -u origin main
git push origin --all
git push origin --tags

echo "Migration complete!"
echo "Verify the repository and update team"

# Compare commit counts
cd /path/to/hg-repo
hg log | grep "changeset:" | wc -l

cd /path/to/git-repo
git log --oneline | wc -l

# Compare branches
hg branches
git branch -a

# Compare tags
hg tags
git tag -l

# Check specific commit
hg log -r <revision>
git show <commit-hash>

# List Mercurial branches
cd /path/to/hg-repo
hg branches

# After migration, Mercurial branches become Git branches
cd /path/to/git-repo
git branch -a

# Rename default branch if needed
git branch -m default main

# Initial migration
git clone hg::/path/to/hg-repo git-repo

cd git-repo

# Later, fetch new changes
git pull hg::/path/to/hg-repo

# Or with hg-fast-export
cd git-repo
../fast-export/hg-fast-export.sh -r /path/to/hg-repo --force

# List Mercurial subrepositories
cd /path/to/hg-repo
cat .hgsub

# Each subrepo needs separate migration
# Then add as Git submodules
cd /path/to/git-repo
git submodule add https://github.com/user/subrepo.git path/to/subrepo

# Remove Mercurial-specific files
cd git-repo
rm -rf .hg .hgignore .hgtags .hgsub .hgsubstate

# Convert .hgignore to .gitignore
# Mercurial uses regex, Git uses glob patterns
# Manual conversion required

# Example .hgignore
syntax: glob
*.pyc
*.log

# Becomes .gitignore
*.pyc
*.log

git add .gitignore
git commit -m "Add .gitignore converted from .hgignore"

# For team members to switch to Git

# 1. Clone new Git repository
git clone https://github.com/user/repo.git

# 2. Remove old Mercurial checkout
rm -rf old-hg-repo

# 3. Configure Git
git config user.name "Your Name"
git config user.email "[email protected]"

# 4. Learn Git workflow
# - git pull instead of hg pull && hg update
# - git push instead of hg push
# - git checkout -b feature instead of hg branch feature

# Mercurial to Git Command Mapping

| Mercurial                 | Git                          |
|--------------------------|------------------------------|
| hg clone                 | git clone                    |
| hg pull && hg update     | git pull                     |
| hg commit                | git commit -a                |
| hg push                  | git push                     |
| hg status                | git status                   |
| hg diff                  | git diff                     |
| hg log                   | git log                      |
| hg branch feature        | git checkout -b feature      |
| hg merge                 | git merge                    |
| hg rollback              | git reset --soft HEAD^       |
| hg branches              | git branch                   |
| hg tags                  | git tag                      |

# If migration fails with encoding errors
export PYTHONIOENCODING=utf-8
hg-fast-export.sh -r /path/to/hg-repo

# If large files cause issues
# Remove large files from history first
hg convert --filemap filemap old-repo new-repo

# filemap content:
# exclude path/to/large/file

# Check Git repository integrity
cd git-repo
git fsck --full

# Verify all commits are reachable
git log --all --oneline | wc -l

# Check for missing objects
git count-objects -v