Migration from SVN to Git

1. SVN to Git migration – migrating subversion to git

Migrating your project from an older VCS to Git- “subversion to git version”

In this section we will learn how can we move svn to git.

Migrating your repository from SVN to Git varies in complexity from one repo to another depending on how old your repository and how many branches and tags is created and merged.

There are many tools such as svn2git available to perform the migration, in this tutorial we will focus on git-svn utility: a Git extension , which can be used to check out a Subversion repository to a local Git repository and then push changes from the local Git repository back to the Subversion repository. 

Pre-requisite:

sudo apt-get install git-core git-svn

High-level overview:

Step 1: Prepping the environment

Step 2: Clone the the source SVN repo to a local git repo : git-svn

Step 3: Copy the same ignore list of SVN as .gitignore list

Step 4: Push temp repo to a bare repository

Step 5: Push local git repository to the new bare repository

Step 6: Clean up branches and tags

Step 7: Move bare repository to central remote repository

Step 8: Share the url and clone this repo on local machine

Svn to git migration steps in detail:

Step 1: Prepping the environment

• Get a list of SVN author names(committers)

Subversion just uses the username for each commit, while Git stores both a real name and an email address.

SVN:

r1 | username | 2016-04-11 92:48:05 +0000 (Mon, 23 Aug 2015)

Git:

Author: username <username@example.com>

This command will retrieve all the log messages, extract the usernames, eliminate any duplicate usernames, sort the usernames, and place them into a "svnAuthors.txt" file. 

cd svn_repo
:svn_repo $svn log -q | grep -e '^r' | awk 'BEGIN { FS = "|" } ; { print $2 }' |
 sort | uniq > svnAuthors.txt

convert from svn format to git format list of author names

A sample shell script to automate the svn to git author names formatting:

Launch the script:

temp $ls
svn2git.sh           svnCommitters.txt

temp $./svn2git.sh

USAGE: [./svn2git.sh] [ svnCommitters.txt ] [ Dir ]

Temp $./svn2git.sh svnCommitters.txt .

Input file:

cat svnAuthors.txt

Sparrow

Earnest

User3

Output file: 

git/gitCommiterList.txt

cat gitCommiterList.txt
Jack Sparrow<sparrow@dos.com>
Earnest Strong<earn@millenium.com>
User three&lt;user3@domain.com&gt;

Step 2: Clone the the source SVN repo to a local git repo : git-svn 

cd ~/temp
git svn clone [SVN repo URL] --prefix=svn/ --no-metadata -A git/gitCommiterList.txt --stdlayout ~/temp
example:
git svn clone ~/svn_repo --prefix=svn/ --no-metadata -A git/gitCommiterList.txt --stdlayout ~/tempRepo

--stdlayout : If you are using the standard trunk, branches, tags layout

--no-metatdata: This gets rid of the git-svn-id: lines at the end of every commit.

Step 3: Copy the same ignore list of SVN as .gitignore list

cd ~/tempRepo
git svn show-ignore > .gitignore

--Add and commit to the local repository
git add .gitignore
git commit -m 'Convert svn:ignore properties to .gitignore'

Step 4: Push temp repo to a bare repository

--Create a bare repository
git init --bare ~/bare-repo.git
cd bare-repo.git

--Make default branch match svn’s trunk branch name
git symbolic-ref HEAD refs/heads/trunk

Step 5: Push local git repository to the new bare repository

--Create a remote handler between local git repo and bare git repository
cd ~/tempRepo
git remote add bare ~/bare-repo.git

git config remote.bare.push ‘refs/remotes/*:refs/heads/*’
git push bare

--Rename ‘trunk’ name to ‘master’
cd ~/bare-repo.git
git branch -m trunk master

Step 6: Clean up branches and tags

svn makes all of Subversions tags into very-short branches in Git of the form "tags/name".

Convert all those branches into actual git tags or delete them.

cd ~/bare-repo.git
git for-each-ref --format='%(refname)' refs/heads/tags |
cut -d / -f 4 |
while read ref
do
 git tag "$ref" "refs/heads/tags/$ref";
 git branch -D "tags/$ref";
done

Step 7: Move bare repository to central remote repository

--Rename bare repository to central repository
mv ~/bare-repo.git central_repo.git

--Create a tar ball to compress the central repo
tar czvf central_repo.git.tar.gz central_repo.git

--Transfer the tar central repo on to the host remote server
scp central_repo.git.tar.gz user1@centos.com:/tmp/

--Connect via ssh to host server
ssh user1@centos.com
cd /tmp/

--Un-tar the central repository on host server
tar xzvf central_repo.git.tar.gz

--Change ownership to all git users for this central repository
sudo chown -R git:staff central_repo.git

--Also remove group and world permissions recursively for this repo
cd central_repo.git
find . -type f -exec chmod go= {} \;
find . -type d -exec chmod go= {} \;

--Move the repo to the project folder path.
cd ../
mv central_repo.git /Users/git/repos/

Step 8: Share the url and clone this repo on local machine

cd ~projDir/
git clone user1@centos.com/tmp/central_repo.git .

All the project contributors will clone the new svn-git transformed repository by cloning as shown in step 8 and start working on the same data as before but now on git repository.

This concludes the svn to github migration.