Migrating from Git to Darcs: Step-by-Step WorkflowMigrating a repository from Git to Darcs can be a strategic choice when you want a patch-based DVCS that treats changes as first-class objects and offers a more flexible history manipulation model. This guide walks through a practical, step-by-step workflow for migrating a single-project Git repository to Darcs, covering preparation, migration methods, verifying integrity, handling branches and tags, dealing with large files, and best practices for team adoption.

Before you start — considerations and prerequisites

• Ensure you have local backups of the Git repository: a bare clone or an archive.
• Install required tools on your workstation:
  • Git (for export and comparisons)
  • Darcs (stable release; darcs executable)
  • Optional: darcs-fastconvert (if available) or scripts that help convert histories
• Decide whether you need full history or only the current state plus a limited history window.
• Understand differences:
  • Darcs is patch-oriented; history manipulation (reordering, cherry-picking) works differently than Git.
  • Darcs does not use SHA-1 commit hashes the way Git does; mapping between identities will change.

Migration strategies — choose one

1. Export current working tree only (fastest, simplest)

   • Use when history is not required or when migrating a legacy project where only the latest state matters.

2. Import full Git history into Darcs (more complex)

   • Use when preserving per-commit history is important.

3. Hybrid: import a limited window of history or important tagged releases plus current state

   • Use when you want some history but not the entire Git timeline.

Option A — Quick migrate (current state only)

1. Create a fresh Darcs repository:

   mkdir myproject-darcs cd myproject-darcs darcs init 

2. Export the current Git working tree:

   # from the git repo root git archive --format=tar HEAD | (cd ../myproject-darcs && tar xf -) 

   If you prefer a simple copy:

   git checkout --force HEAD rsync -a --exclude='.git' ./ ../myproject-darcs/ 

3. Record the initial Darcs patch (add and record):

   cd ../myproject-darcs darcs add . darcs record -am "Initial import from Git: HEAD" 

4. Verify:

   darcs log darcs whatsnew 

This produces a Darcs repository with a single initial patch representing the current state.

Option B — Full history import (recommended when history matters)

Darcs and Git have fundamentally different models; there’s no built-in one-step converter in Darcs core that perfectly replicates Git history. However, there are practical approaches:

• Use darcs-fastconvert (if available) or third-party scripts to convert Git history into a series of Darcs patches.
• Alternatively, write a script that iterates through Git commits in chronological order, checking out each commit, and recording a corresponding Darcs patch.

Warning: preserving author metadata, dates, and complex branching/merge histories may be lossy or require careful scripting.

Method 1 — darcs-fastconvert (if available)

1. Install darcs-fastconvert (check package repos or build from source).

2. Convert:

   # Example (tool-specific flags may differ) darcs-fastconvert git /path/to/git/repo /path/to/output/darcs/repo 

3. Inspect output Darcs repo:

   cd /path/to/output/darcs/repo darcs log 

4. Fix metadata manually if needed (authors, dates).

Method 2 — Commit-by-commit replay (portable)

This method replays Git commits into Darcs as sequential patches. It’s slower but transparent.

1. Prepare:

   git clone --no-hardlinks /path/to/original.git /tmp/git-for-darcs cd /tmp/git-for-darcs # ensure linear history view (use rev-list) 

2. Iterate commits in chronological order and apply them to a fresh Darcs repo: “`bash

   from a script (bash pseudocode)

   GIT_REPO=/tmp/git-for-darcs DARCS_REPO=/tmp/darcs-repo git -C “$GIT_REPO” rev-list –reverse –all > /tmp/commits.txt

mkdir “\(DARCS_REPO" cd "\)DARCS_REPO” darcs init

while read commit; do git -C “\(GIT_REPO" checkout –quiet "\)commit” rsync -a –delete –exclude=‘.git’ “\(GIT_REPO"/ ./ darcs addremove # adds new files, removes deleted AUTHOR=\)(git -C “\(GIT_REPO" show -s –format=’%an <%ae>’ \)commit) MESSAGE=\((git -C "\)GIT_REPO” show -s –format=‘%s’ \(commit) darcs record –author="\)AUTHOR” -m “$MESSAGE” –allow-empty done < /tmp/commits.txt

Notes: - Use git show to get full commit message (subject + body) if desired. - This approach linearizes history; merges become a sequence of commits — merge topology is not preserved. - For large repos, consider filtering or batching. --- ## Handling branches, tags and merges - Branches: Darcs treats patches as exchangeable; you can maintain separate Darcs repositories per branch or replay each Git branch into its own Darcs repo. - Tags: Export Git tags and create corresponding Darcs tags by recording a short descriptive patch or using darcs tag if available. - Merges: Git merge commits will be replayed as normal patches; Darcs has more advanced conflict resolution semantics—expect to manually resolve some complex merges. Example: create Darcs tags from Git tags ```bash git tag -l | while read t; do   git checkout --quiet "$t"   # create a darcs tag by recording a patch that notes the tag   darcs record -am "Tag import: $t" done 

Large files and binary assets

• Darcs stores patches and may be less efficient for very large binary blobs compared to Git LFS. Consider:
  • Splitting large binaries into separate artifact storage (S3, artifact repo).
  • Using darcs-bigfiles (if available) or storing binaries outside the repo.

Verifying integrity and functional parity

• Run test suites and CI against the Darcs repo to ensure builds and behavior are identical.

• Compare file checksums of HEAD between Git and Darcs:

  # In git repo git ls-tree -r HEAD --name-only | sort > /tmp/git-files.txt # In darcs repo find . -type f -not -path "./_darcs/*" | sort > /tmp/darcs-files.txt # Compare lists and locate differences diff /tmp/git-files.txt /tmp/darcs-files.txt 

• Spot-check history: compare commit messages, authors, and timestamps where preserved.

Best practices for team adoption

• Communicate changes and provide training: Darcs concepts (patches, adding/recording, repo interaction) differ from Git.
• Create migration guidelines: how to fetch updates, contribute patches, and handle branches.
• Freeze changes during migration or coordinate cutover to avoid losing recent commits.
• Keep the Git repo as read-only archive for a transition period.

Troubleshooting common issues

• Conflicts during replay: manually resolve in the working tree, then darcs record.
• Missing authors/dates: ensure your script passes –author and sets DARCS_METADATA appropriately (some manual editing might be needed).
• Performance on large histories: consider pruning history, migrating only recent commits, or splitting into modules.

Example migration checklist

• [ ] Backup Git repo (bare clone)
• [ ] Decide migration strategy (full vs. snapshot)
• [ ] Install darcs and conversion tools
• [ ] Test conversion on a copy
• [ ] Verify file-level parity and run test suite
• [ ] Migrate tags/branches as required
• [ ] Communicate with team and schedule cutover
• [ ] Archive old Git repo as read-only

Migrating from Git to Darcs requires careful planning and testing, especially if you want to preserve history. For most projects, exporting the current state into an initial Darcs patch is simplest and lowest-risk; for history preservation, scripted replay or conversion tools work but expect some loss of Git-specific topology and some manual cleanup.