tools: Add a git-svn bootstrap script

[bwidawsk]

Summary

Here is a sample with -n (dry run):

bwidawsk@jai-white:~ (master *$) ~/usr/src/tools/tools/git/git-svn-init -n
Cloning src
git clone git://github.com/freebsd/freebsd.git -o upstream freebsd/src
cd: freebsd/src: No such file or directory
git svn init -Thead --rewrite-root=svn+ssh://svn.freebsd.org/base svn+ssh://repo.freebsd.org/base .
git config --add svn-remote.svn.pushurl svn+ssh://repo.freebsd.org/base
Look for the following:

[svn-remote "svn"]
        url = svn+ssh://repo.freebsd.org/XXX
        rewriteRoot = svn+ssh://svn.freebsd.org/XXX
        pushurl = svn+ssh://repo.freebsd.org/XXX
        fetch = head:refs/remotes/upstream/trunk

git update-ref refs/remotes/upstream/trunk
git svn fetch
git config --add remote.upstream.fetch +refs/pull/*:refs/remotes/upstream/pull/*
git fetch
git svn rebase
Cloning ports
git clone git://github.com/freebsd/freebsd-ports.git -o upstream freebsd/ports
cd: freebsd/ports: No such file or directory
git svn init -Thead --rewrite-root=svn+ssh://svn.freebsd.org/ports svn+ssh://repo.freebsd.org/ports .
git config --add svn-remote.svn.pushurl svn+ssh://repo.freebsd.org/ports
Look for the following:

[svn-remote "svn"]
        url = svn+ssh://repo.freebsd.org/XXX
        rewriteRoot = svn+ssh://svn.freebsd.org/XXX
        pushurl = svn+ssh://repo.freebsd.org/XXX
        fetch = head:refs/remotes/upstream/trunk

git update-ref refs/remotes/upstream/trunk b3503ff80b9c5c0e47e502b95966dec6c1c46dfe
git svn fetch
git config --add remote.upstream.fetch +refs/pull/*:refs/remotes/upstream/pull/*
git fetch
git svn rebase

Suggested by: Warner Losh (imp)

Test Plan

Once my SSH key is added to freebsd.org, I will test that src repo is
setup correctly

[bwidawsk]

Minor fixes and tested now.

[emaste]

Approved, we can get additional testing with it in tree.