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.

README.markdown

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

git-sync-with-svn.sh

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+# -*- mode: Shell-script-*-
+#!/usr/bin/bash
+#
+# Author: Mario Fernandez
+#
+# Syncs git repository with subversion, using an extra git client.
+#
+# The client is a clone of the git repo. It has two branches:
+#  - master: It is sync'ed with the git repo. Should always
+#            fast-forward.
+#  - GIT_SVN_SYNC_BRANCH: Sync'ed with SVN (via git-svn). Noone else
+#            can write to svn.
+#
+# The changes from the git repo are pulled into master, and then
+# merged to the svn sync branch. This branch is then synchronized with
+# subversion.
+#
+# Required environment variabless:
+#  - GIT_SCRIPTS: directory where the git sync scripts are located
+#  - GIT_SVN_SYNC_BASE: directory where the sync repositories are
+# stored.
+#  - GIT_SVN_SYNC_BRANCH: name of the branch that is synchronized with
+# subversion.
+#
+# Usage: git-sync-with-svn.sh project_name
+
+destination=receiver@host.com
+project=${1?No project provided}
+location=${GIT_SVN_SYNC_BASE}/${project}
+
+if [ ! -d $location ] ; then
+    echo "The folder where the synchronization repository is supposed to be does not exist"
+    exit 1
+fi
+
+unset GIT_DIR
+cd $location
+
+report () {
+    echo $1
+    sh ${GIT_SCRIPTS}/report-error.sh $destination "$project" "$1"
+}
+
+# Get changes from git repository
+echo "Getting changes from git repository"
+git checkout master || { report "Could not switch to master" ; exit 1; }
+
+if [ -n "$(git status --porcelain)" ] ; then
+    echo "Workspace is dirty. Clean it up (i.e with git reset --hard HEAD) before continuing"
+    exit 1
+fi
+
+git pull --ff-only origin master || { report "Could not pull changes from git repository" ; exit 1; }
+
+# Synchronize with SVN
+echo "Synchronizing with SVN"
+git checkout ${GIT_SVN_SYNC_BRANCH} || { report "Could not switch to sync branch" ; exit 1; }
+# In case of conflicts, take the master, as we are sure that this is
+# the correct branch
+git merge -Xtheirs master || { report "Could not merge changes into sync branch" ; exit 1; }
+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-*-
+#!/usr/bin/bash
+#
+# Author: Mario Fernandez
+#
+# Initializes a git repository that is synchronized with an existing
+# svn repository.
+#
+# Required environment variabless:
+#  - GIT_SCRIPTS: directory where the git sync scripts are located
+#  - GIT_BASE: directory where the git repositories are
+# stored.
+#  - GIT_SVN_SYNC_BASE: directory where the sync repositories are
+# stored.
+#  - GIT_SVN_SYNC_BRANCH: name of the branch that is synchronized with
+# subversion.
+#
+# Usage: git-repository-from-svn.sh project svn_url
+
+if [ -z "${GIT_SCRIPTS}" ] || [ -z "${GIT_BASE}" ] || [ -z "${GIT_SVN_SYNC_BASE}" ] || [ -z "${GIT_SVN_SYNC_BRANCH}" ] ; then
+    echo "The following variables are required for the synchronization to work: GIT_SCRIPTS GIT_SVN_SYNC_BASE GIT_SVN_SYNC_BRANCH"
+    exit 1
+fi
+
+project=${1?No project name provided}
+svn_url=${2?No svn url provided}
+location=${GIT_BASE}/${project}.git
+client=${GIT_SVN_SYNC_BASE}/${project}
+
+if [ -d $location ] ; then
+    echo "The folder for the git server already exists"
+    exit 1
+fi
+
+if [ -d $client ] ; then
+    echo "The folder for the git sync client already exists"
+    exit 1
+fi
+
+# Git Server
+git init --bare ${location} || { echo "Could not initialize git server at ${location}" ; exit 1; }
+
+# Sync client
+git svn clone ${svn_url} ${client} || { echo "Could not clone svn repository at ${svn_url} in ${client}" ; exit 1; }
+
+cd ${client}
+git remote add origin ${location} || { echo "Could not set up server as remote from sync" ; exit 1; }
+git push origin master || { echo "Could not sync client with server" ; exit 1; }
+git branch ${GIT_SVN_SYNC_BRANCH} || { echo "Could not create svn sync branch" ; exit 1; }
+
+# Set up hooks
+for hook in pre-receive post-receive ; do
+    ln -s ${GIT_SCRIPTS}/server-hooks/${hook} ${location}/hooks
+done
+
+for hook in pre-receive pre-commit ; do
+    ln -s ${GIT_SCRIPTS}/sync-client-hooks/always-reject ${client}/.git/hooks/${hook}
+done

report-error.sh

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

server-hooks/post-receive

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

server-hooks/pre-receive

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

sync-client-hooks/always-reject

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