第9章：邪恶的submodule

基础知识

在worktree内部创建新的repo/worktree是坏的，因为一个文件受两个repo管辖。 一个workaround是将这个小的repo/worktree变成大repo的一个submodule。

一个submodule的信息可以分为静态与动态两大部分，总共分散在5个位置：

• .gitmodules文件中包含一部分静态信息：

  • submodule (name)：名字

  • path：应该放在worktree的哪个路径里面

  • url：在哪里能够找到包含该commit的repo

  • branch：没有什么卵用

  • update：如何处理下级repo的更改

• index中包含另一部分静态信息：

  • commit：上级repo期待哪个commit

• .git/config文件中包含一部分动态信息：

  • submodule (name)

  • active：启用/禁用

  • url

  • update

• .git/modules/<name>/是下级repo，包含一部分动态信息

• <path>是下级repo的worktree，包含一部分动态信息

git config --global alias.lg "log --graph --pretty=tformat:'%h -%d <%an/%cn> %s' --abbrev-commit"

添加/更新submodule的静态部分（.gitmodules/index）

非常简单，直接修改.gitmodules和index：

• Lv1

git init parent
# Initialized empty Git repository in /root/parent/.git/
cd parent
cat - >.gitmodules <<EOF
[submodule "static/name"]
    path = whatever/path
    url = https://github.com/b1f6c1c4/git-get.git
    update = none
EOF
git config --file=.gitmodules --list
# submodule.static/name.path=whatever/path
# submodule.static/name.url=https://github.com/b1f6c1c4/git-get.git
# submodule.static/name.update=none
git update-index --add --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path
git ls-files -s
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path

• Lv2

(rm -rf parent)
git init parent
# Initialized empty Git repository in /root/parent/.git/
cd parent
git config --file=.gitmodules submodule.static/name.path whatever/path
git config --file=.gitmodules submodule.static/name.url https://github.com/b1f6c1c4/git-get.git
git config --file=.gitmodules submodule.static/name.update none
cat .gitmodules
# [submodule "static/name"]
#     path = whatever/path
#     url = https://github.com/b1f6c1c4/git-get.git
#     update = none
git update-index --add --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path
git ls-files -s
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path

非常遗憾的是，没有Lv3的方法能够做到这一点。

用.gitmodules来更新.git/config

• Lv2

cd parent
git config --type=bool submodule.static/name.active true
git config submodule.static/name.url \
  "$(git config --file=.gitmodules submodule.static/name.url)"
git config submodule.static/name.update \
  "$(git config --file=.gitmodules submodule.static/name.update)"
cat .git/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
# [submodule "static/name"]
#     active = true
#     url = https://github.com/b1f6c1c4/git-get.git
#     update = none

• Lv3

cd parent
(git config --remove-section submodule.static/name)
git submodule init -- whatever/path
# Submodule 'static/name' (https://github.com/b1f6c1c4/git-get.git) registered for path 'whatever/path'
cat .git/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
# [submodule "static/name"]
#     active = true
#     url = https://github.com/b1f6c1c4/git-get.git
#     update = none

用.git/config和index来更新repo和worktree

git submodule update是实现这个功能的Lv3命令。 其基本语法是 git submodule update [--checkout|--rebase|--merge] -- <path> 若未指定那三个选项，其功能根据git config submodule.<name>.update而定，共有5种：

• checkout（此为默认情况）

• rebase

• merge

• none

• !...

下面将分别介绍。

git submodule update --checkout == git clone

• Lv2

cd parent
(git submodule --quiet init -- whatever/path)
git config --list | grep -F submodule.static/name
# submodule.static/name.active=true
# submodule.static/name.url=https://github.com/b1f6c1c4/git-get.git
# submodule.static/name.update=none
# 首先创建repo和worktree
mkdir -p .git/modules/static/name
git init --separate-git-dir .git/modules/static/name whatever/path
# Initialized empty Git repository in /root/parent/.git/modules/static/name/
git -C whatever/path config core.worktree ../../../../whatever/path
ls -A .git/modules/static/name whatever/path
# .git/modules/static/name:
# HEAD
# branches
# config
# description
# hooks
# info
# objects
# refs
#
# whatever/path:
# .git
# 然后设置remote
git -C whatever/path remote add origin \
  "$(git config submodule.static/name.url)"
# 然后fetch
git -C whatever/path fetch origin
# From https://github.com/b1f6c1c4/git-get
#  * [new branch]      example-repo0 -> origin/example-repo0
#  * [new branch]      example-repo1 -> origin/example-repo1
#  * [new branch]      example-repo2 -> origin/example-repo2
#  * [new branch]      example/repo3 -> origin/example/repo3
#  * [new branch]      master        -> origin/master
#  * [new tag]         v0.0          -> v0.0
# 然后创建默认分支（根据远端的HEAD是谁而决定）
# （其实这一步实际上并没有什么卵用）
git -C whatever/path symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/master
git -C whatever/path update-ref refs/heads/master refs/remotes/origin/master
git -C whatever/path config branch.master.remote origin
git -C whatever/path config branch.master.merge refs/heads/master
# 然后switch到目标commit
git -C whatever/path switch --detach \
  "$(git ls-files -s -- whatever/path | awk "{ print $2; }")"
# fatal: invalid reference: 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path
git -C whatever/path branch -av
# * master                       e822073 improve PKGBUILD quality
#   remotes/origin/HEAD          -> origin/master
#   remotes/origin/example-repo0 bff56f7 basics
#   remotes/origin/example-repo1 e97348c dummy commit
#   remotes/origin/example-repo2 2dd50b6 use https
#   remotes/origin/example/repo3 2dd50b6 use https
#   remotes/origin/master        e822073 improve PKGBUILD quality
ls -A whatever/path
# .git
cat .git/modules/static/name/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
#     worktree = ../../../../whatever/path
# [remote "origin"]
#     url = https://github.com/b1f6c1c4/git-get.git
#     fetch = +refs/heads/*:refs/remotes/origin/*
# [branch "master"]
#     remote = origin
#     merge = refs/heads/master

由于其中有git fetch，巨量无关数据一并被下载了下来。

• Lv3

cd parent
(rm -rf .git/modules whatever/path)
git submodule update --checkout -- whatever/path
# Cloning into '/root/parent/whatever/path'...
# Submodule path 'whatever/path': checked out 'bff56f7a1c9585780950dce5c1964410e0aa2ecc'
git -C whatever/path branch -av
# * (HEAD detached at bff56f7)   bff56f7 basics
#   master                       e822073 improve PKGBUILD quality
#   remotes/origin/HEAD          -> origin/master
#   remotes/origin/example-repo0 bff56f7 basics
#   remotes/origin/example-repo1 e97348c dummy commit
#   remotes/origin/example-repo2 2dd50b6 use https
#   remotes/origin/example/repo3 2dd50b6 use https
#   remotes/origin/master        e822073 improve PKGBUILD quality
ls -A whatever/path
# .git
# dir
# file
# link
cat .git/modules/static/name/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
#     worktree = ../../../../whatever/path
# [remote "origin"]
#     url = https://github.com/b1f6c1c4/git-get.git
#     fetch = +refs/heads/*:refs/remotes/origin/*
# [branch "master"]
#     remote = origin
#     merge = refs/heads/master

这里面依然有git fetch。 为了解决这个问题，可以使用git-get：

• Lv5: git-get

git submodule update --checkout [-f] == git switch [-f] <commit>

假设index发生了变动：

git -C parent update-index --cacheinfo 160000,e97348c1ba3072a1c108218f6ba88c3177a7456f,whatever/path

• Lv2

cd parent
git -C whatever/path switch -f --detach \
  "$(git ls-files -s -- whatever/path | awk "{ print $2; }")"
# fatal: invalid reference: 160000 e97348c1ba3072a1c108218f6ba88c3177a7456f 0    whatever/path
git -C whatever/path status
# HEAD detached at bff56f7
# nothing to commit, working tree clean

• Lv3

cd parent
git submodule update --checkout -f -- whatever/path
# Submodule path 'whatever/path': checked out 'e97348c1ba3072a1c108218f6ba88c3177a7456f'
git -C whatever/path status
# HEAD detached at e97348c
# nothing to commit, working tree clean

git submodule update --rebase == git rebase <commit>

（先回到原来的HEAD位置）

(git -C parent update-index --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path)
(git -C parent submodule --quiet update --checkout -f -- whatever/path)

假设repo中HEAD发生了变动：

cd parent
git -C whatever/path switch --detach 2dd5
# Previous HEAD position was bff56f7 basics
# HEAD is now at 2dd50b6 use https

然后index又发生了变动：

git -C parent update-index --cacheinfo 160000,e97348c1ba3072a1c108218f6ba88c3177a7456f,whatever/path

现在希望能够把下级repo中新的改动rebase到e973上：

• Lv2

cd parent
git -C whatever/path lg HEAD e973
# * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 2dd50b6 - (HEAD, origin/example/repo3, origin/example-repo2) <b1f6c1c4/b1f6c1c4> use https
# | * 1beea7d - <b1f6c1c4/b1f6c1c4> add repo2 to xsub
# |/  
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics
GIT_COMMITTER_NAME=committer \
GIT_COMMITTER_EMAIL=[e-mail] \
GIT_COMMITTER_DATE='1514736120 +0800' \
git -C whatever/path rebase --quiet e973
git -C whatever/path lg HEAD e973
# * d02f6d7 - (HEAD) <b1f6c1c4/committer> use https
# * c4a760b - <b1f6c1c4/committer> add repo2 to xsub
# * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics

• Lv3

cd parent
(git -C whatever/path switch --detach 2dd5 2>/dev/null)
git -C whatever/path lg HEAD e973
# * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 2dd50b6 - (HEAD, origin/example/repo3, origin/example-repo2) <b1f6c1c4/b1f6c1c4> use https
# | * 1beea7d - <b1f6c1c4/b1f6c1c4> add repo2 to xsub
# |/  
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics
GIT_COMMITTER_NAME=committer \
GIT_COMMITTER_EMAIL=[e-mail] \
GIT_COMMITTER_DATE='1514736120 +0800' \
git submodule update --rebase -- whatever/path 2>/dev/null
# Submodule path 'whatever/path': rebased into 'e97348c1ba3072a1c108218f6ba88c3177a7456f'
git -C whatever/path lg HEAD e973
# * d02f6d7 - (HEAD) <b1f6c1c4/committer> use https
# * c4a760b - <b1f6c1c4/committer> add repo2 to xsub
# * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics

git submodule update --merge == git merge <commit>

（先回到原来的HEAD位置）

(git -C parent update-index --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path)
(git -C parent submodule update --checkout -f -- whatever/path 2>/dev/null)
# Submodule path 'whatever/path': checked out 'bff56f7a1c9585780950dce5c1964410e0aa2ecc'

假设repo中HEAD发生了变动：

cd parent
git -C whatever/path switch --detach 2dd5
# Previous HEAD position was bff56f7 basics
# HEAD is now at 2dd50b6 use https

然后index又发生了变动：

git -C parent update-index --cacheinfo 160000,e97348c1ba3072a1c108218f6ba88c3177a7456f,whatever/path

现在希望能够在下级repo中merge上级以为的新的改动：

• Lv2

cd parent
git -C whatever/path lg HEAD e973
# * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 2dd50b6 - (HEAD, origin/example/repo3, origin/example-repo2) <b1f6c1c4/b1f6c1c4> use https
# | * 1beea7d - <b1f6c1c4/b1f6c1c4> add repo2 to xsub
# |/  
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics
GIT_AUTHOR_NAME=author \
GIT_AUTHOR_EMAIL=[e-mail] \
GIT_AUTHOR_DATE='1234567890 +0800' \
GIT_COMMITTER_NAME=committer \
GIT_COMMITTER_EMAIL=[e-mail] \
GIT_COMMITTER_DATE='1514736120 +0800' \
git -C whatever/path merge e973
# Already up to date!
# Merge made by the 'recursive' strategy.
git -C whatever/path lg HEAD e973
# *   46b15af - (HEAD) <author/committer> Merge commit 'e973' into HEAD
# |\  
# | * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# | * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# | * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# * | 2dd50b6 - (origin/example/repo3, origin/example-repo2) <b1f6c1c4/b1f6c1c4> use https
# * | 1beea7d - <b1f6c1c4/b1f6c1c4> add repo2 to xsub
# |/  
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics

• Lv3

cd parent
(git -C whatever/path switch --quiet --detach 2dd5)
git -C whatever/path lg HEAD e973
# * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 2dd50b6 - (HEAD, origin/example/repo3, origin/example-repo2) <b1f6c1c4/b1f6c1c4> use https
# | * 1beea7d - <b1f6c1c4/b1f6c1c4> add repo2 to xsub
# |/  
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics
GIT_AUTHOR_NAME=author \
GIT_AUTHOR_EMAIL=[e-mail] \
GIT_AUTHOR_DATE='1234567890 +0800' \
GIT_COMMITTER_NAME=committer \
GIT_COMMITTER_EMAIL=[e-mail] \
GIT_COMMITTER_DATE='1514736120 +0800' \
git submodule update --merge -- whatever/path
# Already up to date!
# Merge made by the 'recursive' strategy.
# Submodule path 'whatever/path': merged in 'e97348c1ba3072a1c108218f6ba88c3177a7456f'
git -C whatever/path lg HEAD e973
# *   71e724c - (HEAD) <author/committer> Merge commit 'e97348c1ba3072a1c108218f6ba88c3177a7456f' into HEAD
# |\  
# | * e97348c - (origin/example-repo1) <b1f6c1c4/b1f6c1c4> dummy commit
# | * ac33e9e - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 7fffa2c - <b1f6c1c4/b1f6c1c4> dummy commit
# | * db89c7a - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 58e8a67 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * a37e16b - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 329a265 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * eec9c41 - <b1f6c1c4/b1f6c1c4> dummy commit
# | * 3c19b79 - <b1f6c1c4/b1f6c1c4> dummy commit
# * | 2dd50b6 - (origin/example/repo3, origin/example-repo2) <b1f6c1c4/b1f6c1c4> use https
# * | 1beea7d - <b1f6c1c4/b1f6c1c4> add repo2 to xsub
# |/  
# * 2c0d59d - <b1f6c1c4/b1f6c1c4> use https
# * e7b2ae8 - <b1f6c1c4/b1f6c1c4> add repo0 to sub
# * bff56f7 - (origin/example-repo0) <b1f6c1c4/b1f6c1c4> basics

其他两种git config submodule.<name>.update

cd parent
git config submodule.static/name.update none
git submodule update -- whatever/path
# Skipping submodule 'whatever/path'

cd parent
git config submodule.static/name.update '!true'
git submodule update -- whatever/path
# Submodule path 'whatever/path': 'true e97348c1ba3072a1c108218f6ba88c3177a7456f'
git config submodule.static/name.update '!false'
git submodule update -- whatever/path
# Execution of 'false e97348c1ba3072a1c108218f6ba88c3177a7456f' failed in submodule path 'whatever/path'
git config submodule.static/name.update '!echo'
git submodule update -- whatever/path
# e97348c1ba3072a1c108218f6ba88c3177a7456f
# Submodule path 'whatever/path': 'echo e97348c1ba3072a1c108218f6ba88c3177a7456f'

用.gitmodules和index来创建repo和worktree

分两步：用.gitmodules来更新.git/config；再用.git/config和index来更新repo和worktree。 Lv2不再赘述。

• Lv3

cd parent
(rm -rf .git/modules whatever/path)
git submodule update --init --checkout -- whatever/path
# Cloning into '/root/parent/whatever/path'...
# Submodule path 'whatever/path': checked out 'e97348c1ba3072a1c108218f6ba88c3177a7456f'

用repo来更新index

（先回到原来的HEAD位置）

(git -C parent update-index --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path)
(git -C parent submodule --quiet update --checkout -f -- whatever/path)

假设repo中HEAD发生了变动：

cd parent
git -C whatever/path switch --detach 2dd5
# Previous HEAD position was bff56f7 basics
# HEAD is now at 2dd50b6 use https

现在希望index也跟着变动：

• Lv1

cd parent
git ls-files -s
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path
git update-index --cacheinfo "160000,$(git -C whatever/path rev-parse HEAD),whatever/path"
git ls-files -s
# 160000 2dd50b6425c7d79f4695aa69d05467e1a00fc20f 0    whatever/path

• Lv2

cd parent
(git update-index --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path)
git ls-files -s
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path
git update-index -- whatever/path
git ls-files -s
# 160000 2dd50b6425c7d79f4695aa69d05467e1a00fc20f 0    whatever/path

• Lv3

cd parent
(git update-index --cacheinfo 160000,bff56f7a1c9585780950dce5c1964410e0aa2ecc,whatever/path)
git ls-files -s
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path
git add whatever/path
git ls-files -s
# 160000 2dd50b6425c7d79f4695aa69d05467e1a00fc20f 0    whatever/path

用.gitmodules来更新.git/config和repo的URL

cd parent
git config --file=.gitmodules submodule.static/name.url https://localhost

• Lv2

cd parent
git config submodule.static/name.url \
  "$(git config --file=.gitmodules submodule.static/name.url)"
git -C whatever/path remote set-url origin \
  "$(git config --file=.gitmodules submodule.static/name.url)"

• Lv3

cd parent
git submodule sync -- whatever/path
# Synchronizing submodule url for 'whatever/path'
git config --get submodule.static/name.url
# https://localhost
git -C whatever/path remote -v
# origin    https://localhost (fetch)
# origin    https://localhost (push)

一次性添加.gitmodules、.git/config、index、repo、worktree

• Lv2

先添加.gitmodules和index，然后用.gitmodules更新.git/config， 然后用.git/config和index创建repo和worktree。

• Lv3

注意：只能指定一个branch，不能指定某个commit。 包括git fetch，可能造成大量资源浪费。

(rm -rf parent && git init --quiet parent)
cd parent
git submodule add -b example-repo0 -f --name static/name -- https://github.com/b1f6c1c4/git-get.git whatever/path
# Cloning into '/root/parent/whatever/path'...
cat .gitmodules
# [submodule "static/name"]
#     path = whatever/path
#     url = https://github.com/b1f6c1c4/git-get.git
#     branch = example-repo0
cat .git/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
# [submodule "static/name"]
#     url = https://github.com/b1f6c1c4/git-get.git
#     active = true
git ls-files -s
# 100644 64817d5b42c4ac1087a41478d37dfe22df2bacad 0    .gitmodules
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path
ls -A .git/modules/static/name
# HEAD
# branches
# config
# description
# hooks
# index
# info
# logs
# objects
# packed-refs
# refs
ls -A whatever/path
# .git
# dir
# file
# link

删除.git/config和worktree

• Lv2

cd parent
git config --remove-section submodule.static/name
rm -rf whatever/path

• Lv3

cd parent
(git submodule --quiet update --init -- whatever/path)
git submodule deinit -f -- whatever/path
# Cleared directory 'whatever/path'
# Submodule 'static/name' (https://github.com/b1f6c1c4/git-get.git) unregistered for path 'whatever/path'
cat .gitmodules
# [submodule "static/name"]
#     path = whatever/path
#     url = https://github.com/b1f6c1c4/git-get.git
#     branch = example-repo0
cat .git/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
git ls-files -s
# 100644 64817d5b42c4ac1087a41478d37dfe22df2bacad 0    .gitmodules
# 160000 bff56f7a1c9585780950dce5c1964410e0aa2ecc 0    whatever/path
ls -A .git/modules/static/name
# HEAD
# branches
# config
# description
# hooks
# index
# info
# logs
# objects
# packed-refs
# refs
ls -A whatever/path

删除.gitmodules和index

• Lv2

cd parent
git config --file=.gitmodules --remove-section submodule.static/name
git update-index --force-remove whatever/path
rm -rf whatever/path
git update-index -fu -- whatever/path
# error: unknown switch 'f'
# usage: git update-index [<options>] [--] [<file>...]
# 
#     -q                    continue refresh even when index needs update
#     --ignore-submodules   refresh: ignore submodules
#     --add                 do not ignore new files
#     --replace             let files replace directories and vice-versa
#     --remove              notice files missing from worktree
#     --unmerged            refresh even if index contains unmerged entries
#     --refresh             refresh stat information
#     --really-refresh      like --refresh, but ignore assume-unchanged setting
#     --cacheinfo <mode>,<object>,<path>
#                           add the specified entry to the index
#     --chmod (+|-)x        override the executable bit of the listed files
#     --assume-unchanged    mark files as "not changing"
#     --no-assume-unchanged
#                           clear assumed-unchanged bit
#     --skip-worktree       mark files as "index-only"
#     --no-skip-worktree    clear skip-worktree bit
#     --ignore-skip-worktree-entries
#                           do not touch index-only entries
#     --info-only           add to index only; do not add content to object database
#     --force-remove        remove named paths even if present in worktree
#     -z                    with --stdin: input lines are terminated by null bytes
#     --stdin               read list of paths to be updated from standard input
#     --index-info          add entries from standard input to the index
#     --unresolve           repopulate stages #2 and #3 for the listed paths
#     -g, --again           only update entries that differ from HEAD
#     --ignore-missing      ignore files missing from worktree
#     --verbose             report actions to standard output
#     --clear-resolve-undo  (for porcelains) forget saved unresolved conflicts
#     --index-version <n>   write index in this format
#     --split-index         enable or disable split index
#     --untracked-cache     enable/disable untracked cache
#     --test-untracked-cache
#                           test if the filesystem supports untracked cache
#     --force-untracked-cache
#                           enable untracked cache without testing the filesystem
#     --force-write-index   write out the index even if is not flagged as changed
#     --fsmonitor           enable or disable file system monitor
#     --fsmonitor-valid     mark files as fsmonitor valid
#     --no-fsmonitor-valid  clear fsmonitor valid bit
# 
cat .gitmodules
cat .git/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
git ls-files -s
# 100644 64817d5b42c4ac1087a41478d37dfe22df2bacad 0    .gitmodules
ls -A .git/modules/static/name
# HEAD
# branches
# config
# description
# hooks
# index
# info
# logs
# objects
# packed-refs
# refs
ls -A whatever/path
# ls: cannot access 'whatever/path': No such file or directory

• Lv3

cd parent
(git submodule --quiet add -b example-repo0 -f --name static/name -- https://github.com/b1f6c1c4/git-get.git whatever/path)
# Reactivating local git directory for submodule 'static/name'.
git config --file=.gitmodules --remove-section submodule.static/name
git rm -f whatever/path
# fatal: please stage your changes to .gitmodules or stash them to proceed
# 注意：git rm -f 要求先 git add .gitmodules
git add .gitmodules
git rm -f whatever/path
# warning: Could not find section in .gitmodules where path=whatever/path
# rm 'whatever/path'
cat .gitmodules
cat .git/config
# [core]
#     repositoryformatversion = 0
#     filemode = true
#     bare = false
#     logallrefupdates = true
# [submodule "static/name"]
#     url = https://github.com/b1f6c1c4/git-get.git
#     active = true
git ls-files -s
# 100644 e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 0    .gitmodules
ls -A .git/modules/static/name
# HEAD
# branches
# config
# description
# hooks
# index
# info
# logs
# objects
# packed-refs
# refs
ls -A whatever/path
# ls: cannot access 'whatever/path': No such file or directory

非常遗憾的是，repo必须手工rm -rf。

由repo和worktree创建.gitmodules和index

假设如此创建repo和worktree：

(rm -rf parent && git init --quiet parent)
cd parent
git clone https://github.com/b1f6c1c4/git-get.git whatever/path
# Cloning into 'whatever/path'...

现在欲将parent/whatever/path纳入parent当成submodule管理。

• Lv2

cd parent
git config --file=.gitmodules submodule.static/name.path whatever/path
git config --file=.gitmodules submodule.static/name.url \
  "$(git -C whatever/path config --get remote.origin.url)"
git update-index --add --cacheinfo "160000,$(git -C whatever/path rev-parse HEAD),whatever/path"
git -C whatever/path config core.worktree ../../../../whatever/path
mkdir -p .git/modules/static/
mv whatever/path/.git .git/modules/static/name
echo 'gitdir: ../../.git/modules/static/name' > whatever/path/.git
git submodule status
# -e8220732efb5151bb9428a625f14827e3d4eeeb9 whatever/path

• Lv3

(rm -rf parent && git init parent)
# Initialized empty Git repository in /root/parent/.git/
cd parent
(git clone --quiet https://github.com/b1f6c1c4/git-get.git whatever/path)
# 遗憾的是，没有办法简化前几步
git config --file=.gitmodules submodule.static/name.path whatever/path
git config --file=.gitmodules submodule.static/name.url \
  "$(git -C whatever/path config --get remote.origin.url)"
git update-index --add --cacheinfo "160000,$(git -C whatever/path rev-parse HEAD),whatever/path"
git submodule absorbgitdirs -- whatever/path
# Migrating git directory of 'whatever/path' from
# '/root/parent/whatever/path/.git' to
# '/root/parent/.git/modules/static/name'
git submodule status
# -e8220732efb5151bb9428a625f14827e3d4eeeb9 whatever/path

总结

• 一次性添加submodule的五个部分：

  • git submodule add [-b <branch>] [--name <name>] -- <url> <path>

• 分别修改submodule的五个部分：

  • .gitmodules

    • Lv0: vim .gitmodules

    • Lv2: git config --file=.gitmodules submodule.<name>.<key> <value>

  • $GIT_DIR/config

    • Lv0: vim .git/config

    • Lv2: git config submodule.<name>.<key> <value>

  • index

    • Lv2：git update-index [--add|--force-remove] --cacheinfo 160000,<sha1>,<path>

  • repo ($GIT_DIR/modules/<name>)

    • git -C <path> ...

  • worktree ($GIT_WORK_TREE/<path>)

    • git -C <path> ...

• 用静态更新动态：

  • git submodule init -- <path>

    • 用.gitmodules来更新.git/config

  • git submodule update --init [--recursive] --checkout -- <path>

    • 用.gitmodules和index来创建repo和worktree

  • git submodule sync -- <path>

    • 用.gitmodules来更新.git/config和repo的URL

  • git gets -- <path>

    • 快速下载指定commit

• 用静态和动态更新动态：

  • git submodule update [--recursive] [--checkout|--rebase|--merge] -- <path>

    • 用.git/config和index来更新repo和worktree，共5种选项

• 用动态更新静态：

  • git update-index -- <path> - 用repo来更新index

  • git add <path> - 用repo来更新index

  • git submodule absorbgitdirs -- <path>

    • 有repo、worktree、.gitmodules和index之后，用该命令创建.git/config并将repo移动到正确位置

• 删除：

  • git submodule deinit -f -- <path>

    • 删除.git/config和worktree

  • 其他部分需要逐一删除