イメージ的には、svn externals



$ cd <sfproject>
$ mkdir -p lib/vendor
$ git submodule add git:// lib/vendor/symfony
Cloning into lib/vendor/symfony...
remote: Counting objects: 5247, done.
remote: Compressing objects: 100% (2611/2611), done.
remote: Total 5247 (delta 2383), reused 5037 (delta 2226)
Receiving objects: 100% (5247/5247), 4.12 MiB | 308 KiB/s, done.
Resolving deltas: 100% (2383/2383), done.
$ git ci -m 'import symfony'
[master (root-commit) 688aee2] import symfony
 2 files changed, 4 insertions(+), 0 deletions(-)
 create mode 100644 .gitmodules
 create mode 160000 lib/vendor/symfony
$ git st
# On branch master
nothing to commit (working directory clean)
# 確認
$ php lib/vendor/symfony/data/bin/symfony -V
symfony version 1.4.12-DEV (<sfproject>/lib/vendor/symfony/lib)
# タスク一覧
$ php lib/vendor/symfony/data/bin/symfony -vT
  symfony [options] task_name [arguments]

  --help                   -H  Display this help message.
  --quiet                  -q  Do not log messages to standard output.
  --trace                  -t  Turn on invoke/execute tracing, enable full backtrace.
  --version                -V  Display the program version.
  --color                      Forces ANSI color output.
  --xml                        To output help as XML