clone ceph的submodules

[submodule "ceph-object-corpus"]
path = ceph-object-corpus
url = https://github.com/ceph/ceph-object-corpus.git [submodule "src/civetweb"]
path = src/civetweb
url = https://github.com/ceph/civetweb [submodule "src/erasure-code/jerasure/jerasure"]
path = src/erasure-code/jerasure/jerasure
url = https://github.com/ceph/jerasure.git branch = v2-ceph
[submodule "src/erasure-code/jerasure/gf-complete"]
path = src/erasure-code/jerasure/gf-complete
url = https://github.com/ceph/gf-complete.git branch = v2-ceph
[submodule "src/rocksdb"]
path = src/rocksdb
url = https://github.com/ceph/rocksdb ignore = dirty
[submodule "ceph-erasure-code-corpus"]
path = ceph-erasure-code-corpus
url = https://github.com/ceph/ceph-erasure-code-corpus.git [submodule "src/gmock"]
path = src/gmock
url = https://github.com/ceph/gmock.git branch = ceph-release-1.7.0
[submodule "src/spdk"]
path = src/spdk
url = https://github.com/ceph/spdk.git [submodule "src/xxHash"]
path = src/xxHash
url = https://github.com/ceph/xxHash.git[/code]你可以通过执行这个命令clone所有的代码 
git clone --recursive https://github.com/ceph/ceph.git[/code]如果你clone代码时没有加--recursive这个选项，默认是不会clone所有的modules，如果你需要这些module，你也可以通过以下命令，把他们clone下来。 
git submodule update --init --recursive