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Save your sources; From legacy SVN to modern Git

Hi there “Process Automation” fans,

Welcome to a new installment of “Process Automation” tips.

What we did last week between two SVN brokers, we now do from SVN (VisualSVN) to GitHub. How difficult can it be!? It’s always good to know and understand what needs to happen. Somewhere in the future it’ll be your task to execute it, and you’ll be prepared with this post. Enjoy the pain and sweat…😅

Again (like last week), two things are important in this exercise:

  1. Our repository with the solution sources of OPA should be intact
  2. The history of our commits (incl. messages) should be intact

Let’s get right into it…

Right, we start off to see what we have in VisualSVN currently (the result from last week viewed in TortoiseSVN):

svn_git_001

Let’s move this (incl. that history) to GitHub; it’s a private repo online under my GitHub account:

svn_git_002

The URL we eventually need is https://github.com/HetBenkt/OPA_REPO_GITHUB.git

If you get stuck on GitHub, read this and this

All ready? Let’s move from SVN to GIT…

WAIT…First read this post before running any commands, as Git is picky on two important topics from what we’ve eXperienced:

  1. Authors in Git have an email address; you can use a mapping file authors.txt
  2. Empty folders in SVN require at least one file; use .gitkeep. Or better, .identifiers, as that’s what the platform does on empty folders once you’re connected to Git!

Move from VisualSVN to GitHub

My VisualSVN server is on my local laptop, so we’re using CMD prompts to make it happen! First make sure you have the git -v command available to get a response like git version 2.45.2.windows.1. If you don’t have it, install it first.

This Git CLI has a nice tool to move from SVN to Git: git svn <command> [options] [arguments]. We just need to figure out how it works…

Let’s first do a validation check like this: "C:\Program Files\VisualSVN Server\bin\svn" ls https://192.168.56.1/svn/OPA_REPO_VISUALSVN/prj_generic. It should list your project content.

If all is fine, give this command: git svn clone https://192.168.56.1/svn/OPA_REPO_VISUALSVN/prj_generic --prefix=svn/ prj_generic-git

Permanently accept the certificate details and provide the credentials for the SVN repo. Some logging will pass by, and you’ll end up with a new folder prj_generic-git at the location executing the command.

Go into the folder cd prj_generic-git and check if all is fine:

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git log --oneline --all --graph --decorate
git branch -a

The current branch name is now master which we’ll update to main via git branch -M main.

SVN can also work with branches AND also with tags; however, we kept our project simple without them. Git always works in one branch! If you also want to save/convert your SVN branches/tags, have a look at these commands (I leave them out of scope for this post!):

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git branch -r
git branch some-branch svn/branches/some-branch
git branch -r | grep tags
git tag v1.0 svn/tags/v1.0

We’re ready locally, let’s now add a remote location via: git remote add origin https://github.com/HetBenkt/OPA_REPO_GITHUB.git

Finally, we can push our local Git remotely via: git push -u origin main. You need to provide your GitHub credentials (not your password, but a token!) to make it work. Create a new so-called “fine-grained” token in the developer settings of your GitHub account!

svn_git_003

Make sure to set the permission for this token to the correct repo with sufficient permissions:

svn_git_004

If you’re using branches/tags in SVN:

  • This will push branches: git push origin some-branch
  • This will push tags: git push origin --tags

After that push, you’ll see this in your new GitHub repo (incl. commit history!):

svn_git_005

Looking at one of the commits gives me a satisfying result as it also saved the user details:

svn_git_006

If you see weird user details (like svnuser <svnuser@...>) it’s better to create an authors.txt file with this content:

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opadev = OPA Developer <antal@bos-ictservices.nl>
someuser = Some User <someuser@example.com>

You can pass it into the git svn clone... command via --authors-file=authors.txt. Have a look at this fully enriched command (incl. trunk, branches, tags, and authors):

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git svn clone https://192.168.56.1/svn/OPA_REPO_VISUALSVN --trunk=prj_generic/trunk --branches=prj_generic/branches --tags=prj_generic/tags --prefix=svn/ --authors-file=authors.txt prj_generic-git

So far an excellent job! Let’s see if OPA likes/accepts our new repo in GitHub from a new workspace:

svn_git_007

#OMG…That’s a failure! However, we can learn from it:

svn_git_008

What is wrong here? Well, because of the heat (here in the Netherlands) I didn’t see (some screenshots back) the missing folders! Why are they missing? Well, in my project they’re empty AND GitHub doesn’t like to maintain “empty” folders! How to solve? Well, before doing the migration commands, ask your developers to add .gitkeep files in the empty folders. This way you have a solid solution that will always work. Do remember that we (as low-code developers) are not under control of what is saved in SCM. So, make sure your SVN sources are complete on empty folders, unlocked, and ready for migration.

…

These are the quick steps on how I solved my current situation:

  1. Create a new file in PowerShell locally: New-Item .gitkeep -type file
  2. Upload it to the empty folder of the project and commit the changes in SVN:

svn_git_009

  1. Go into your remotely attached Git repo location cd prj_generic-git
  2. Run git svn fetch to collect the SVN changes into your new Git repo (in the main branch!)
  3. Merge the changes via: git merge --ff-only refs/remotes/svn/git-svn
  4. Push all changes remotely: git push origin main
  5. Double-check the result:

svn_git_010

After this fix, it was another (similar) issue…Watch closely! Yes, I miss a parent folder prj_generic! So, in quick commands:

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cd prj_generic-git
mkdir prj_generic
# I copy/paste in Windows Explorer everything (except the .git folder) into the new folder
git add -A
git commit -m "Move project files into prj_generic folder"
git push origin main

…

After the fixing section, it’s a party where all is working fine now; I added the ‘Lifecycle’ BB to the migrated ‘Case’ entity with a solid commit into Git! 🥳
I even tried an empty folder and checked the outcome in Git after a commit; it looks like the platform uses a file .identifiers to fill up the empty folder. After some Git browsing, I even conclude OPA adds this file in every folder (incl. the ones that do have content). So, I would not even upload those .gitkeep files to the project via the UI. I would add them already in the prj_generic-git location, push them remotely, and then create a new workspace, as those .identifiers files have a special magic touch during OPA commits.

Good to know that you can now also move on with TortoiseGit…a simple task to eXperience on your own!

Move from GitHub to VisualSVN

WHAT? Why on earth would you ever want to move from Git to SVN!?!? Comment below if you’re that person, and I’ll update the post for it!

That’s again a great migration “DONE”, where we moved our valuable solution data from SVN to GIT. It’s not that hard if you know how to accomplish such a task; now you know! Share it with your colleagues and we’ll continue the eXperience next week in another topic about Process Automation Tips…cheers! 🍺

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