gitea-svn-mirror

Py sidecar SVN↔Git bidirectional mirror for Gitea. Uses own mapping DB (not git svn) so Git commit hashes never change.

Architecture

┌──────────────┐   SVN poll    ┌──────────────────┐
│   SVN remote │ ◄───────────  │  svn-mirror       │
│  (http/svn+) │ ────────────► │  daemon / sync    │
└──────────────┘               │                   │
                               │  ┌──────────────┐ │
┌──────────────┐   git push    │  │ canonical    │ │
│   Gitea      │ ◄───────────  │  │ bare repo    │ │
│  (webhook)   │ ────────────► │  └──────────────┘ │
└──────────────┘   git fetch   │                   │
                               │  SQLite mapping   │
                               └──────────────────┘

• Canonical bare repo: the single source of truth on the Git side
• Mapping DB: SQLite table (svn_revision, svn_branch) ↔ git_commit_hash
• SVN WC: per-branch working copy checked out for applying Git→SVN diffs
• Daemon: polls SVN on interval, pushes Git→SVN on webhook or interval

Requirements

• Python 3.11+
• git + git-svn (for one-time git svn clone --no-metadata during init)
• svn CLI (Subversion client)
• Gitea instance (bare repos accessible on disk, not just via HTTP API)

Install system deps

# Debian / Ubuntu
apt install python3 python3-pip git git-svn subversion

# RHEL / Rocky / Alma
yum install python3 python3-pip git git-svn subversion

Installation

# Clone
git clone https://github.com/your-org/svn-git-server /opt/svn-git-server
cd /opt/svn-git-server

# Install Python deps
pip install -r requirements.txt

Only dependency: PyYAML. The rest is stdlib + CLI tools.

Configuration

Create /etc/svn-mirror/config.yml:

data_dir: /var/svn-mirror

mirrors:
  - id: my-project
    enabled: true

    svn:
      url: https://svn.example.com/svn/myproject
      layout: std              # "std" for standard /trunk /branches /tags
      # For non-standard layout:
      # layout: custom
      # trunk: trunk
      # branches: branches
      # tags: tags

    gitea:
      owner: myorg
      repo: myproject
      repos_path: /var/lib/gitea/data/repositories  # path to Gitea's bare repos
      webhook_secret: "choose-a-random-secret"      # shared HMAC secret
      webhook_host: "0.0.0.0"
      webhook_port: 8080

    authors:
      "john": "John Doe <john@example.com>"
      "jane": "Jane Doe <jane@example.com>"

    sync_interval: 120   # SVN→Git poll interval (seconds)

repos_path — finding Gitea's repos on disk

The sidecar accesses Gitea's repos on disk, not via HTTP API. Find the path:

Setup	Typical path
Gitea binary	/var/lib/gitea/data/repositories
Gitea Docker	/data/git/repositories
git user home	/home/git/repositories

If unset the tool tries common defaults. Set it explicitly to be safe.

Quick start

1. Validate config

python -m svn_mirror check --config /etc/svn-mirror/config.yml

2. Create mirror directories

python -m svn_mirror create --mirror my-project --config /etc/svn-mirror/config.yml

Creates {data_dir}/mirrors/{id}/ with:

• canonical-repo.git — bare Git repo
• mapping.db — SQLite mapping DB
• state.json — mirror state
• sync.lock — flock-based concurrency lock

3. Initial SVN import

python -m svn_mirror init --mirror my-project --config /etc/svn-mirror/config.yml

Runs git svn clone --no-metadata (one-time bootstrap), then tears down git-svn metadata. All ongoing sync is handled by the tool's own engine.

4. Sync SVN → Git

python -m svn_mirror sync --mirror my-project --config /etc/svn-mirror/config.yml

5. Push Git → SVN

python -m svn_mirror push --mirror my-project --config /etc/svn-mirror/config.yml

6. Check status

python -m svn_mirror status --mirror my-project --config /etc/svn-mirror/config.yml

Deployment modes

Mode A: Polling daemon (simple)

python -m svn_mirror daemon --config /etc/svn-mirror/config.yml

Polls SVN every sync_interval seconds. Pushes new Git commits to SVN on the same interval.

systemd unit

# /etc/systemd/system/svn-mirror.service
[Unit]
Description=gitea-svn-mirror daemon
After=network-online.target

[Service]
Type=simple
ExecStart=/usr/bin/python3 -m svn_mirror daemon --config /etc/svn-mirror/config.yml
Restart=always
User=root
WorkingDirectory=/opt/svn-git-server

[Install]
WantedBy=multi-user.target

systemctl daemon-reload
systemctl enable --now svn-mirror

Mode B: Webhook-only (event-driven)

python -m svn_mirror webhook --config /etc/svn-mirror/config.yml

Listens for Gitea push webhooks on POST /webhook. When a push arrives it fetches the new commits from Gitea and runs sync_git_to_svn.

Gitea webhook config: Go to repo → Settings → Webhooks → Add:

• Target URL: http://your-server:8080/webhook
• Secret: same as webhook_secret in config
• Events: "Push"

Mode C: Both (recommended)

Run daemon AND webhook. The daemon handles SVN→Git polling; the webhook handles instant Git→SVN on developer push.

python -m svn_mirror daemon --config /etc/svn-mirror/config.yml &
python -m svn_mirror webhook --config /etc/svn-mirror/config.yml &

Reconciliation (fixing divergence)

If the sync was interrupted (daemon down for days) and commits landed on both SVN and Git independently, the tool can re-sync them.

# 1. Assess divergence (dry-run, no changes)
python -m svn_mirror reconcile --assess --mirror my-project --config /etc/svn-mirror/config.yml

# 2. Reconcile (creates SVN commit merging Git changes into SVN)
python -m svn_mirror reconcile --mirror my-project --config /etc/svn-mirror/config.yml

# 3. Normal sync to bring Git in line
python -m svn_mirror sync --mirror my-project --config /etc/svn-mirror/config.yml

The reconciliation:

• Backs up the mapping DB
• Applies each Git developer commit (not yet in DB) onto the SVN trunk WC
• Commits to SVN as a single [reconcile] revision
• Records the mapping so sync_git_to_svn doesn't re-push those commits
• Leaves last_svn_revision unchanged — sync processes pending SVN revisions naturally

Dry-run mode:

python -m svn_mirror reconcile --dry-run --mirror my-project --config /etc/svn-mirror/config.yml

Shows the assessment report and what would be done, without making any changes.

All commands

Command	Description
check	Validate config and prerequisites
create	Create mirror directory structure
init	Run git svn clone initial import
destroy	Delete all mirror data
status	Show mirror status
sync	Bidirectional sync (SVN→Git + Git→SVN)
push	Git→SVN direction only
daemon	Continuous polling loop
webhook	Gitea webhook receiver
reconcile	Fix divergence (see above)

File layout

{data_dir}/mirrors/{id}/
├── canonical-repo.git/      # bare Git repo (canonical Git copy)
├── mapping.db               # SQLite mapping DB
├── state.json               # mirror metadata
├── authors.txt              # git svn authors file
├── sync.lock                # flock-based concurrency lock
└── svn-wc/                  # SVN working copies (per branch)

Caveats

• Binary files: supported (fix in sync.py uses raw bytes for hash-object)
• Empty directories: SVN tracks them, Git does not — skipped during sync
• Large repos: initial git svn clone time depends on SVN history size
• One trunk only: reconciliation only handles refs/heads/master ↔ SVN trunk. Other branches are not yet supported by the reconcile tool.