184 lines
7 KiB
Markdown
184 lines
7 KiB
Markdown
# Migrating from SVN to GitLab
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Subversion (SVN) is a central version control system (VCS) while
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Git is a distributed version control system. There are some major differences
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between the two, for more information consult your favorite search engine.
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## Overview
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There are two approaches to SVN to Git migration:
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1. [Git/SVN Mirror](#smooth-migration-with-a-git-svn-mirror-using-subgit) which:
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- Makes the GitLab repository to mirror the SVN project.
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- Git and SVN repositories are kept in sync; you can use either one.
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- Smoothens the migration process and allows to manage migration risks.
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1. [Cut over migration](#cut-over-migration-with-svn2git) which:
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- Translates and imports the existing data and history from SVN to Git.
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- Is a fire and forget approach, good for smaller teams.
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## Smooth migration with a Git/SVN mirror using SubGit
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[SubGit](https://subgit.com) is a tool for a smooth, stress-free SVN to Git
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migration. It creates a writable Git mirror of a local or remote Subversion
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repository and that way you can use both Subversion and Git as long as you like.
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It requires access to your GitLab server as it talks with the Git repositories
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directly in a filesystem level.
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### SubGit prerequisites
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1. Install Oracle JRE 1.8 or newer. On Debian-based Linux distributions you can
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follow [this article](http://www.webupd8.org/2012/09/install-oracle-java-8-in-ubuntu-via-ppa.html).
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1. Download SubGit from <https://subgit.com/download/>.
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1. Unpack the downloaded SubGit zip archive to the `/opt` directory. The `subgit`
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command will be available at `/opt/subgit-VERSION/bin/subgit`.
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### SubGit configuration
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The first step to mirror you SVN repository in GitLab is to create a new empty
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project which will be used as a mirror. For Omnibus installations the path to
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the repository will be located at
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`/var/opt/gitlab/git-data/repositories/USER/REPO.git` by default. For
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installations from source, the default repository directory will be
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`/home/git/repositories/USER/REPO.git`. For convenience, assign this path to a
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variable:
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```
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GIT_REPO_PATH=/var/opt/gitlab/git-data/repositories/USER/REPOS.git
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```
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SubGit will keep this repository in sync with a remote SVN project. For
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convenience, assign your remote SVN project URL to a variable:
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```
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SVN_PROJECT_URL=http://svn.company.com/repos/project
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```
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Next you need to run SubGit to set up a Git/SVN mirror. Make sure the following
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`subgit` command is ran on behalf of the same user that keeps ownership of
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GitLab Git repositories (by default `git`):
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```
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subgit configure --layout auto $SVN_PROJECT_URL $GIT_REPO_PATH
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```
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Adjust authors and branches mappings, if necessary. Open with your favorite
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text editor:
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```
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edit $GIT_REPO_PATH/subgit/authors.txt
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edit $GIT_REPO_PATH/subgit/config
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```
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For more information regarding the SubGit configuration options, refer to
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[SubGit's documentation](https://subgit.com/documentation/) website.
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### Initial translation
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Now that SubGit has configured the Git/SVN repos, run `subgit` to perform the
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initial translation of existing SVN revisions into the Git repository:
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```
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subgit install $GIT_REPO_PATH
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```
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After the initial translation is completed, the Git repository and the SVN
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project will be kept in sync by `subgit` - new Git commits will be translated to
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SVN revisions and new SVN revisions will be translated to Git commits. Mirror
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works transparently and does not require any special commands.
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If you would prefer to perform one-time cut over migration with `subgit`, use
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the `import` command instead of `install`:
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```
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subgit import $GIT_REPO_PATH
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```
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### SubGit licensing
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Running SubGit in a mirror mode requires a
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[registration](https://subgit.com/pricing/). Registration is free for open
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source, academic and startup projects.
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We're currently working on deeper GitLab/SubGit integration. You may track our
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progress at [this issue](https://gitlab.com/gitlab-org/gitlab-ee/issues/990).
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### SubGit support
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For any questions related to SVN to GitLab migration with SubGit, you can
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contact the SubGit team directly at [support@subgit.com](mailto:support@subgit.com).
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## Cut over migration with svn2git
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If you are currently using an SVN repository, you can migrate the repository
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to Git and GitLab. We recommend a hard cut over - run the migration command once
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and then have all developers start using the new GitLab repository immediately.
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Otherwise, it's hard to keep changing in sync in both directions. The conversion
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process should be run on a local workstation.
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Install `svn2git`. On all systems you can install as a Ruby gem if you already
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have Ruby and Git installed.
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```bash
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sudo gem install svn2git
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```
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On Debian-based Linux distributions you can install the native packages:
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```bash
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sudo apt-get install git-core git-svn ruby
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```
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Optionally, prepare an authors file so `svn2git` can map SVN authors to Git authors.
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If you choose not to create the authors file then commits will not be attributed
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to the correct GitLab user. Some users may not consider this a big issue while
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others will want to ensure they complete this step. If you choose to map authors
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you will be required to map every author that is present on changes in the SVN
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repository. If you don't, the conversion will fail and you will have to update
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the author file accordingly. The following command will search through the
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repository and output a list of authors.
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```bash
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svn log --quiet | grep -E "r[0-9]+ \| .+ \|" | cut -d'|' -f2 | sed 's/ //g' | sort | uniq
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```
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Use the output from the last command to construct the authors file.
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Create a file called `authors.txt` and add one mapping per line.
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```
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janedoe = Jane Doe <janedoe@example.com>
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johndoe = John Doe <johndoe@example.com>
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```
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If your SVN repository is in the standard format (trunk, branches, tags,
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not nested) the conversion is simple. For a non-standard repository see
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[svn2git documentation](https://github.com/nirvdrum/svn2git). The following
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command will checkout the repository and do the conversion in the current
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working directory. Be sure to create a new directory for each repository before
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running the `svn2git` command. The conversion process will take some time.
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```bash
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svn2git https://svn.example.com/path/to/repo --authors /path/to/authors.txt
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```
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If your SVN repository requires a username and password add the
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`--username <username>` and `--password <password` flags to the above command.
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`svn2git` also supports excluding certain file paths, branches, tags, etc. See
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[svn2git documentation](https://github.com/nirvdrum/svn2git) or run
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`svn2git --help` for full documentation on all of the available options.
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Create a new GitLab project, where you will eventually push your converted code.
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Copy the SSH or HTTP(S) repository URL from the project page. Add the GitLab
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repository as a Git remote and push all the changes. This will push all commits,
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branches and tags.
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```bash
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git remote add origin git@gitlab.com:<group>/<project>.git
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git push --all origin
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git push --tags origin
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```
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## Contribute to this guide
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We welcome all contributions that would expand this guide with instructions on
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how to migrate from SVN and other version control systems.
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