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Mario Fernandez
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Initial commit with the scripts to synchronize git with svn
This contains multiple scripts: - A script to synchronize an existing git repository with subversion via a git synch client - hooks for the git server to trigger the sync after a push - a hook for the client to reject every manual change - A script to create a new git server repository, along with the git synch client, starting from an existing subversion repository.
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‎README.markdown

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# _git_ SVN Sync
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This repository is intended to provide synchronization between a
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running SVN repository and _git_, so that we can get away from
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subversion while the build jobs are ported.
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## Workflow
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The idea is to use pure _git_ exclusively. The subversion repository is
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up to date and used to build artifacts and jars, but nobody is
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expected to write to it except the _git_ sync client.
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Therefore _git_ would be used both at client and server side. This is an
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improvement over using git-svn because it allows to commit branches to
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the server, and avoids rewriting history when commiting to svn, among
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other things.
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## Technical view
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For every project in subversion, two _git_ repositories are created, the
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server and the sync client.
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### _git_ Server
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It is a normal bare repository, which supports every git
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operation. Every developer clones this repository and uses it
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exclusively for the project.
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When someone pushes changes to the master branch, a hook is run which
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uses the sync client to bring the changes to subversion.
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### _git_ Sync client
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This is a repository which is a clone of the _git_ server. When the
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post-receive hook at the server is activated, the following happens at
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this client:
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* Changes are pulled from the server to the master branch.
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* The master branch is merged into a svn sync branch.
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* The changes are sent to subversion via git-svn.
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This repository is not intended for developers to use. It rejects
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every push and commit, and should only automatically sync with the
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server.
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### Maintaining consistency
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The _git_ server and subversion should be in the same state at every
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time. To guarantee this, the following conditions are required:
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* Only the _git_ sync client should ever send changes to
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subversion. The write access to svn should be restricted to the
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remote _git_ user.
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* Nobody except the build jobs in jenkins uses subversion directly
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anymore. Developers interact only with the _git_ server.
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* The _git_ sync client is never modified. It only pulls changes from
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the _git_ server (only fast-forward allowed).
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The consistency is assured via hooks that are installed at the server
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and sync client. Access to subversion has to be configured separately.
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### Reporting
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If something does not work correctly, a mail will be sent specifying
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the project which had the problem and the registered error
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## Setup
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### Initial setup
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The machine where the repositories are installed needs the following
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environment variables (defined in its ~/.bashrc):
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* **GIT_SCRIPTS**: directory where the _git_ sync scripts are located
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* **GIT_BASE**: directory where the _git_ repositories are stored.
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* **GIT_SVN_SYNC_BASE**: directory where the sync repositories are stored.
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* **GIT_SVN_SYNC_BRANCH**: name of the branch that is synchronized
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with subversion.
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This repository should be cloned in the directory **GIT_SCRIPTS**.
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### SVN User
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Git needs to have write access to subversion.
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### Git config
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For the git user that will sync with svn
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git config --global user.email "the@email"
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git config --global user.name "Git User"
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### New project
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Each project in subversion can be initialized with the
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install/git-repository-from-svn.sh script. It makes sure that the
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initial setup is carried and that the hooks are activated.
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‎git-sync-with-svn.sh

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# -*- mode: Shell-script-*-
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#!/usr/bin/bash
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#
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# Author: Mario Fernandez
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#
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# Syncs git repository with subversion, using an extra git client.
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#
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# The client is a clone of the git repo. It has two branches:
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# - master: It is sync'ed with the git repo. Should always
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# fast-forward.
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# - GIT_SVN_SYNC_BRANCH: Sync'ed with SVN (via git-svn). Noone else
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# can write to svn.
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#
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# The changes from the git repo are pulled into master, and then
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# merged to the svn sync branch. This branch is then synchronized with
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# subversion.
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#
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# Required environment variabless:
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# - GIT_SCRIPTS: directory where the git sync scripts are located
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# - GIT_SVN_SYNC_BASE: directory where the sync repositories are
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# stored.
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# - GIT_SVN_SYNC_BRANCH: name of the branch that is synchronized with
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# subversion.
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#
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# Usage: git-sync-with-svn.sh project_name
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[email protected]
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project=${1?No project provided}
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location=${GIT_SVN_SYNC_BASE}/${project}
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if [ ! -d $location ] ; then
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echo "The folder where the synchronization repository is supposed to be does not exist"
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exit 1
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fi
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unset GIT_DIR
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cd $location
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report () {
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echo $1
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sh ${GIT_SCRIPTS}/report-error.sh $destination "$project" "$1"
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}
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# Get changes from git repository
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echo "Getting changes from git repository"
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git checkout master || { report "Could not switch to master" ; exit 1; }
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if [ -n "$(git status --porcelain)" ] ; then
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echo "Workspace is dirty. Clean it up (i.e with git reset --hard HEAD) before continuing"
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exit 1
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fi
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git pull --ff-only origin master || { report "Could not pull changes from git repository" ; exit 1; }
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# Synchronize with SVN
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echo "Synchronizing with SVN"
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git checkout ${GIT_SVN_SYNC_BRANCH} || { report "Could not switch to sync branch" ; exit 1; }
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# In case of conflicts, take the master, as we are sure that this is
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# the correct branch
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git merge -Xtheirs master || { report "Could not merge changes into sync branch" ; exit 1; }
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git svn dcommit || { report "Could not send changes to svn repository" ; exit 1; }

‎install/git-repository-from-svn.sh

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# -*- mode: Shell-script-*-
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#!/usr/bin/bash
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#
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# Author: Mario Fernandez
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#
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# Initializes a git repository that is synchronized with an existing
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# svn repository.
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#
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# Required environment variabless:
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# - GIT_SCRIPTS: directory where the git sync scripts are located
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# - GIT_BASE: directory where the git repositories are
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# stored.
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# - GIT_SVN_SYNC_BASE: directory where the sync repositories are
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# stored.
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# - GIT_SVN_SYNC_BRANCH: name of the branch that is synchronized with
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# subversion.
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#
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# Usage: git-repository-from-svn.sh project svn_url
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if [ -z "${GIT_SCRIPTS}" ] || [ -z "${GIT_BASE}" ] || [ -z "${GIT_SVN_SYNC_BASE}" ] || [ -z "${GIT_SVN_SYNC_BRANCH}" ] ; then
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echo "The following variables are required for the synchronization to work: GIT_SCRIPTS GIT_SVN_SYNC_BASE GIT_SVN_SYNC_BRANCH"
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exit 1
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fi
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project=${1?No project name provided}
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svn_url=${2?No svn url provided}
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location=${GIT_BASE}/${project}.git
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client=${GIT_SVN_SYNC_BASE}/${project}
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if [ -d $location ] ; then
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echo "The folder for the git server already exists"
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exit 1
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fi
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if [ -d $client ] ; then
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echo "The folder for the git sync client already exists"
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exit 1
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fi
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# Git Server
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git init --bare ${location} || { echo "Could not initialize git server at ${location}" ; exit 1; }
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# Sync client
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git svn clone ${svn_url} ${client} || { echo "Could not clone svn repository at ${svn_url} in ${client}" ; exit 1; }
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cd ${client}
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git remote add origin ${location} || { echo "Could not set up server as remote from sync" ; exit 1; }
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git push origin master || { echo "Could not sync client with server" ; exit 1; }
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git branch ${GIT_SVN_SYNC_BRANCH} || { echo "Could not create svn sync branch" ; exit 1; }
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# Set up hooks
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for hook in pre-receive post-receive ; do
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ln -s ${GIT_SCRIPTS}/server-hooks/${hook} ${location}/hooks
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done
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for hook in pre-receive pre-commit ; do
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ln -s ${GIT_SCRIPTS}/sync-client-hooks/always-reject ${client}/.git/hooks/${hook}
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done

‎report-error.sh

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# -*- mode: Shell-script-*-
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#!/usr/bin/bash
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#
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# Author: Mario Fernandez
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#
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# Sends an email with the error message obtained from syncing a repository.
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destination=${1?No destination provided}
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project=${2?No project provided}
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message=${3?No message provided}
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cat > /tmp/git-sync-failure <<EOF
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The project $project could not be correctly synchronized. The output of the script was:
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$message
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EOF
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subject="Git-SVN failed for project $project"
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mail -s "$subject" $destination < /tmp/git-sync-failure

‎server-hooks/post-receive

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# -*- mode: Shell-script-*-
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#!/usr/bin/bash
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#
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# This hook is intended to be installed for a git server. It calls a
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# script that synchronizes every change with subversion.
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#
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# Required environment variables:
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# - GIT_SCRIPTS: directory where the git sync scripts are located
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#
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# Author: Mario Fernandez
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master="refs/heads/master"
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while read oldrev newrev refname
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do
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if [ "$master" == "$refname" ] ; then
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sh ${GIT_SCRIPTS}/git-sync-with-svn.sh $(basename $PWD .git)
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fi
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done

‎server-hooks/pre-receive

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# -*- mode: Shell-script-*-
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#!/usr/bin/bash
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#
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# This hook is intended to be installed for a git server. It calls a
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# script that synchronizes every change with subversion.
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#
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# Required environment variables:
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# - GIT_SCRIPTS: directory where the git sync scripts are located
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#
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# Author: Mario Fernandez
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if [ -z "${GIT_SCRIPTS}" ] || [ -z "${GIT_SVN_SYNC_BASE}" ] || [ -z "${GIT_SVN_SYNC_BRANCH}" ] ; then
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echo "The following variables are required for the synchronization to work: GIT_SCRIPTS GIT_SVN_SYNC_BASE GIT_SVN_SYNC_BRANCH"
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exit 1
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fi
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while read oldrev newrev refname
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do
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if [ "$refname" == "${GIT_SVN_SYNC_BRANCH}" ] ; then
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echo "It is not allowed to push a branch named ${GIT_SVN_SYNC_BRANCH} to avoid conflicts when syncing with subversion"
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exit 1
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fi
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done

‎sync-client-hooks/always-reject

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# -*- mode: Shell-script-*-
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#!/usr/bin/bash
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#
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# Author: Mario Fernandez
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echo "The synchronization client does not accept manual modifications"
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exit 1

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