第3章：直接操纵索引

基础知识

Git索引位于<repo>/index，本质是一个复杂的二进制文件。 具体格式参见这里，大概包括以下内容：

• 路径和文件名

• mode

• stage数（第6章讨论merge时会用到，正常情况为0）

• 修改时间

• 文件大小

• （其他标识文件唯一性的信息）

• 文件内容对应的blob的SHA1

由于直接修改该文件非常复杂，所以本章不介绍Lv0的方案。

如未提前说明，本章所有命令都需要--git-dir和--work-tree。 不过为了避免繁琐的--git-dir和--work-tree，本章所有命令都会在worktree里面执行：

git init .
# Initialized empty Git repository in /root/.git/

也就意味着忽略掉--git-dir和--work-tree也能正常工作。读者需要判断哪些命令可以不依赖--work-tree。

添加/修改index

• Lv1

# 注意：此处故意忽略掉-w，导致blob对象并没有被真正创建
echo 'content' | git hash-object -t blob --stdin
# d95f3ad14dee633a758d2e331151e950dd13e4ed
# blob不一定需要真正存在
git update-index --add --cacheinfo 100644,d95f3ad14dee633a758d2e331151e950dd13e4ed,dir/fn

• Lv2

# 要先有文件才能添加到index
mkdir -p dir
echo 'content' > dir/fn
# 以下命令只修改index，不创建blob
git update-index --add --info-only -- dir/fn
# 以下命令既修改index，也创建blob
git update-index --add -- dir/fn

若想手动改变mode，只需git update-index --chmod +x -- <path>

• Lv3

# 要先有文件才能添加到index
mkdir -p dir
echo 'content' > dir/fn
# 以下命令既修改index，也创建blob
git add -f dir/fn

如果想只添加一部分内容，使用git add -p

删除index

• Lv2

(git add -f dir/fn)
git update-index --force-remove -- dir/fn

• Lv3

(git add -f dir/fn)
git rm --cached -- dir/fn
# rm 'dir/fn'

移动index

没有简单办法。 Lv2方法，使用git update-index --cacheinfo无法指定文件stat信息 Lv3方法，使用git mv不仅移动了index还移动了worktree里的文件

查看index

• Lv2

  （其中0为stage数，正常情况为0）

(git add -f dir/fn)
git ls-files -s
# 100644 d95f3ad14dee633a758d2e331151e950dd13e4ed 0    dir/fn

利用tree更新index

先弄一个tree：

echo 'hello' | git hash-object -t blob --stdin -w
# ce013625030ba8dba906f756967f9e9ca394464a
git mktree --missing <<EOF
100644 blob ce013625030ba8dba906f756967f9e9ca394464a$(printf '\t')name.ext
100755 blob ce013625030ba8dba906f756967f9e9ca394464a$(printf '\t')name2.ext
EOF
# 58417991a0e30203e7e9b938f62a9a6f9ce10a9a

• Lv2

# 整个index替换掉
git read-tree 5841
git ls-files -s
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    name2.ext
# 合并到某个文件夹
(git update-index --force-remove -- name.ext name2.ext && git add -f dir/fn)
git read-tree --prefix=dir/ 5841
git ls-files -s
# 100644 d95f3ad14dee633a758d2e331151e950dd13e4ed 0    dir/fn
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    dir/name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    dir/name2.ext
# 注意特殊情况
(git update-index --force-remove -- dir/fn dir/name.ext dir/name2.ext && git add -f dir/fn)
git read-tree --prefix=dir/fn/ 5841
git ls-files -s
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    dir/fn/name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    dir/fn/name2.ext

• Lv3

# 整个index替换掉
git restore --source 5841 --staged -- :/
git ls-files -s
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    name2.ext
# 替换掉某个文件
(git update-index --force-remove -- name.ext)
git restore --source 5841 --staged -- name.ext
git ls-files -s
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    name2.ext

利用index更新worktree

注意：添加修改都可以，但是无法删除worktree里面多出来的文件。 请参阅本章最后一节（git clean）。

• Lv2

# 整个worktree替换掉
git checkout-index -fu -a
# 全部加前缀（不必是文件夹路径）
git checkout-index --prefix -fu -a
# 只有一部分文件
git checkout-index -fu -- name.ext

• Lv3

# 整个worktree替换掉
git restore --worktree -- :/
# 只有一部分文件
git restore --worktree -- name.ext
# 以下为等价的旧语法
# git checkout -f -- :/
# git checkout -f -- name.ext

利用index创建tree

• Lv2

(git read-tree --prefix=dir/ 5841)
git ls-files -s
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    dir/name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    dir/name2.ext
# 100644 ce013625030ba8dba906f756967f9e9ca394464a 0    name.ext
# 100755 ce013625030ba8dba906f756967f9e9ca394464a 0    name2.ext
# 用整个index创建tree
git write-tree
# 34ade2bb5494b722dea8a9874afddd3562f32744
# 用一个子目录创建tree
git write-tree --prefix=dir/
# 58417991a0e30203e7e9b938f62a9a6f9ce10a9a

注意：当存在非0的stage数时（一般是由git read-tree -m导致的，见第6章），git write-tree会失败

• Lv3

  注意：git commit创建tree并创建commit

(git config --global user.name "b1f6c1c4")
(git config --global user.email "[e-mail]")
git commit --allow-empty -m 'The message'
# [master (root-commit) b43919a] The message
#  4 files changed, 4 insertions(+)
#  create mode 100644 dir/name.ext
#  create mode 100755 dir/name2.ext
#  create mode 100644 name.ext
#  create mode 100755 name2.ext

利用tree更新worktree

• Lv1

# 准备：
echo 0 >f
git add f
git commit -m '0'
# [master 5e2ea31] 0
#  1 file changed, 1 insertion(+)
#  create mode 100644 f
echo 1 >f
git add f
echo 2 >f
# 执行：
git cat-file blob HEAD:f >f
# 检查：
git cat-file blob $(git ls-files -s -- f | awk '{ print $2; }')
# 1
cat f
# 0

• Lv3

# 准备：
echo 0 >f
git add f
git commit -m '0'
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
#     deleted:    dir/name.ext
#     deleted:    dir/name2.ext
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#     -funame.ext
#     -funame2.ext
#     .bashrc
#     .gitconfig
#     .profile
#     dir/fn
#
# no changes added to commit (use "git add" and/or "git commit -a")
echo 1 >f
git add f
echo 2 >f
# 执行：
git restore --source HEAD --worktree -- f
# 检查：
git cat-file blob $(git ls-files -s -- f | awk '{ print $2; }')
# 1
cat f
# 0

利用tree同时更新index和worktree

• Lv2 一步一步来即可

• Lv3

# 准备：
echo 0 >f
git add f
git commit -m '0'
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
#     deleted:    dir/name.ext
#     deleted:    dir/name2.ext
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#     -funame.ext
#     -funame2.ext
#     .bashrc
#     .gitconfig
#     .profile
#     dir/fn
#
# no changes added to commit (use "git add" and/or "git commit -a")
echo 1 >f
git add f
echo 2 >f
# 执行：
git restore --source HEAD --staged --worktree -- f
# 检查：
git cat-file blob $(git ls-files -s -- f | awk '{ print $2; }')
# 0
cat f
# 0

注意：git restore --worktree没有对应的旧语法。

详解git restore

• git restore [--source <tree-ish>] [--staged] [--worktree] -- <path>

  • 若<tree-ish>留空：

    • 不写--staged也不写--worktree：<tree-ish>表示index

    • --worktree：<tree-ish>表示index

    • --staged --worktree：<tree-ish>表示index，而--staged被忽略了

    • --staged：<tree-ish>表示HEAD

  • 不写--staged也不写--worktree则默认--worktree

等价旧语法：

• git restore [--worktree] -- <path>=git checkout -f -- <path>

• git restore --staged --worktree -- <path>=git checkout -f -- <path>

• git restore [--source <tree-ish>] --staged -- <path>=git reset [<tree-ish>] -- <path>

• git restore --source <tree-ish> --staged --worktree -- <path>=git checkout -f <tree-ish> -- <path>

• git restore --source <tree-ish> [--worktree] -- <path> 没有等价的旧语法！

交互式修改index

有时候我们希望将一个文件的部分更改放入index中，此时使用git add -p即可。 如果不小心放多了，使用git restore -p即可。（旧语法git reset -p）

将index和worktree中的更改暂存起来以备日后使用

• Lv3

只需git stash [pop]：

git status
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
#     deleted:    dir/name.ext
#     deleted:    dir/name2.ext
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#     -funame.ext
#     -funame2.ext
#     .bashrc
#     .gitconfig
#     .profile
#     dir/fn
#
# no changes added to commit (use "git add" and/or "git commit -a")
git stash
# Saved working directory and index state WIP on master: 5e2ea31 0
git status
# On branch master
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#     -funame.ext
#     -funame2.ext
#     .bashrc
#     .gitconfig
#     .profile
#     dir/fn
#
# nothing added to commit but untracked files present (use "git add" to track)
git stash pop
# Removing dir/name2.ext
# Removing dir/name.ext
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
#     deleted:    dir/name.ext
#     deleted:    dir/name2.ext
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#     -funame.ext
#     -funame2.ext
#     .bashrc
#     .gitconfig
#     .profile
#     dir/fn
#
# no changes added to commit (use "git add" and/or "git commit -a")
# Dropped refs/stash@{0} (d6ae6279a658b60a3a396fc2db675fcd84dcdb14)
git status
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
#     deleted:    dir/name.ext
#     deleted:    dir/name2.ext
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#     -funame.ext
#     -funame2.ext
#     .bashrc
#     .gitconfig
#     .profile
#     dir/fn
#
# no changes added to commit (use "git add" and/or "git commit -a")

注意：请一定认真检查git stash的输出！ 不要假设git stash总是成功的。 如果git stash没有成功那么你的更改并没有并保存起来！

git stash pop本质是git merge。参见第6章处理冲突。

删除worktree中多出来的文件（git clean）

警告：该命令十分危险，可能一瞬删掉你的全部心血！

touch extra
# 检查多出来了什么文件
git clean -nd
# Would remove -funame.ext
# Would remove -funame2.ext
# Would remove .bashrc
# Would remove .gitconfig
# Would remove .profile
# Would remove dir/fn
# Would remove extra
# 统统删掉
git clean -fd
# Removing -funame.ext
# Removing -funame2.ext
# Removing .bashrc
# Removing .gitconfig
# Removing .profile
# Removing dir/fn
# Removing extra

把以下命令的-n换成-f就能真正删掉文件了 （非常危险，请一定先git clean -n看看什么会消失再真的去-f）：

echo 'fff' >.gitignore
git add .gitignore
touch fff
touch extra
# 准备删掉多出来的non-ignored文件
git clean -nd
# Would remove extra
# 准备删掉多出来的所有文件
git clean -ndx
# Would remove extra
# Would remove fff
# 准备删掉多出来的ignored文件
git clean -ndX
# Would remove fff

总结

• Lv1

  • git update-index --add --cacheinfo <mode>,<SHA1>,<path>

• 不常用Lv2

  • git update-index --add [--info-only] -- <path>

  • git update-index --force-remove -- <path>

  • git checkout-index -fu [--prefix=<pf>] -a

  • git checkout-index -fu [--prefix=<pf>] -- <path>

• 常用Lv2

  • git update-index --chmod +x -- <path>

  • git ls-files -s

  • git ls-files -s -- <path>

  • git read-tree [--prefix=<pf>] <tree-ish>

  • git write-tree [--prefix=<pf>]

• Lv3

  • git add -f -- <path>

  • git rm --cached -- <path>

  • git mv

  • git restore [--source <tree-ish>] [--staged] [--worktree] -- <path>

  • git commit

  • git stash [pop]

  • git clean -nd [-x|-X] [-- <path>]（把-n换成-f就会真的删除，非常危险）

• 交互式修改index

  • git add -p

  • git restore -p