svn及git使用笔记

这周发生好几件大事：

1. 谷歌发布SHA-1安全加密碰撞实例
2. Cloudflare 泄露网络会话中的加密数据
3. linux内核漏洞 CVE-2017-6074

加密在网络中愈来愈受关注，目前github的提交仍然是以SHA-1做为标签的，期待后期改善。

下面是安装使用git的简短记录， 有些翻译不完整

安装

若是须要 Bash 命令补完（也即按下 Tab 来完成你正在键入的命令），请在~/.bashrc文件中添加以下内容：

source /usr/share/git/completion/git-completion.bash

你也能够安装 bash-completion 来自动为 shell 提供命令补完。

若是你想使用 Git 内建的图形界面（例如 gitk 或者 git gui），你须要安装 tk 软件包，不然你会遇到一个隐晦的错误信息：

/usr/bin/gitk: line 3: exec: wish: not found.

配置

Git 从若干 INI 格式的配置文件中读取配置信息。在每个 git 版本库中，.git/config 用于指定与该版本库有关的配置选项。在 $HOME/.gitconfig 中的用户 ("global") 的配置文件将被用做仓库配置的备用配置。你能够直接编辑配置文件，可是更推荐的方法是使用 git-config 工具。例如，

$ git config --global core.editor "nano -w"

会在 ~/.gitconfig 文件的 [core] 部分中添加 editor = nano -w。

git-config 工具的 man page 提供了完整的选项列表。

这是一些你可能用到的常见的配置：

$ git config --global user.name "Firstname Lastname"
$ git config --global user.email "your_email@youremail.com"

在 Git 命令行下启用彩色输出
配置 color.ui 选项能够令 Git 以彩色输出信息。

$ git config --global color.ui true

解决 Git 在命令行下中文文件名显示为数字的问题

$ git config --global core.quotepath false

基本用法

克隆一个版本库

如下命令能够将一个 Git 版本库克隆至本地目录的新文件夹中：

git clone <repo location> <dir>

若是留空

字段，就会以 Git 版本库的名称命名新文件夹，例如：

git clone git@github.com:torvalds/linux.git

能够将 GitHub 上 Linux 内核的镜像克隆至名为「linux」的文件夹中。

提交（commit）文件到版本库
Git 的提交过程分为两步：
添加新文件、修改现有的文件（都可经过 git add 完成), 或者删除文件（经过 git rm 完成）。这些修改将被存入名叫 index 的文件中。

使用 git commit 提交修改。
Git 提交时会打开文本编辑器，填写提交信息。你能够经过 git config 命令修改 core.editor 来选择编辑器。

此外，你也能够直接用 git commit -m 命令在提交时填写提交信息，这样就不会打开编辑器。

其它有用的技巧：

git commit -a lets you commit changes you have made to files already under Git control without having to take the step of adding the changes to the index. You still have to add new files with git add.
git commit -a 命令能够跳过添加修改的部分，可是若是建立新文件依然须要 git add。
git add -p 命令能够提交修改文件的特定部分。若是你进行了许多修改并且但愿将其分屡次提交的话，这一选项很是有用。

将改动提交（push）到公共版本库
如下命令能够将修改提交至服务器（例如 Github）：

git push <server name> <branch>

添加 -u 参数能够将该服务器设为当前分支（branch）提交时的默认服务器。若是你是经过上文的方法克隆的版本库，默认服务器将是你克隆的来源（别名「origin」），默认分支将是 master。也就是说若是你按照上文的方法克隆的话，提交时只要执行 git push 便可。若是须要的话，能够令 Git 提交至多个服务器，不过这比较复杂。下文将讲解分支（branch）。

从服务器公共版本库下载修改
若是你在多台电脑上工做，而且须要将本地版本库与服务器更新，能够执行：

git pull <server name> <branch>

与 push 相似，server name 与 branch 均可以根据默认来，因此只需执行 git pull。
Git pull 其实是以下两个命令的简写：

git fetch，将服务器文件复制至本地，这一分支被称做「remote」也即它是远程服务器的镜像。
git merge，将「remote」分支的文件与本地文件合并。若是你的本地提交记录与服务器的提交记录相同，就能够直接获得服务器的最新版本。若是你的提交记录与服务器的记录不符（例如在你最后一次提交以后别人进行了提交），两份提交记录将被合并。

It is not a bad idea to get into the practice of using these two commands instead of git pull. This way you can check to make sure that the server contains what you would expect before merging.
分步执行两个命令而非 git pull 并非坏事，这样能够确保合并以前服务器的文件与你指望的相同。

查看历史记录
git log 命令能够显示当前分支的历史记录。注意每一次提交（commit）会以一个 SHA-1 标记区分，接下来是提交者、提交日期以及提交信息。更实用的命令：

git log --graph --oneline --decorate

能够显示与 TortoiseGit 的提交记录相似的窗口，这一窗口包含了以下内容：
每次提交的 SHA-1 标记的前七位（足以区分不一样的提交）
--graph 选项能够显示从当前分支 fork 的分支数目（若是有的话）
--oneline 选项能够在一行内显示每次提交的信息
--decorate 选项能够显示全部的提交信息（包括分支与标签）

能够经过以下命令将这一命令以 git graph 的别名保存：

git config --global alias.graph 'log --graph --oneline --decorate'

如今执行 git graph 将等价于执行 git log --graph --oneline --decorate。
git graph 与 git log 命令也能够带 --all 的参数执行，这将显示全部的分支信息，而不止当前的分支。
也能够带 --stat 参数执行，它能够显示每次提交时哪些文件有修改、修改了多少行。

处理合并（merge）
当你执行 pull、进行复原操做，或者将一个分支与另外一个进行合并时会须要处理合并。与其它 VCS 相似，当 Git 没法自动处理合并时，就须要使用者进行处理。
能够查看 Git Book 的这一部分讲解如何处理冲突合并。
若是你须要经过合并来还原的话，能够带 --abort 参数运行合并相关的命令，例如 git merge --abort，git pull --abort，git rebase --abort)。

使用分布式版本控制系统

The above commands only provide the basics. The real power and convenience in Git (and other distributed version control systems) come from leveraging its local commits and fast branching. A typical Git workflow looks like this:
Create and check out a branch to add a feature.
Make as many commits as you would like on that branch while developing that feature.
Squash, rearrange, and edit your commits until you are satisfied with the commits enough to push them to the central server and make them public.
Merge your branch back into the main branch.
Delete your branch, if you desire.
Push your changes to the central server.

建立一个分支

git branch <branch name>

can be used to create a branch that will branch off the current commit. After it has been created, you should switch to it using

git checkout <branch name>

A simpler method is to do both in one step with

git checkout -b <branch name>

To see a list of branches, and which branch is currently checked out, use

git branch

A word on commits
Many of the following commands take commits as arguments. A commit can be identified by any of the following:
Its 40-digit SHA-1 hash (the first 7 digits are usually sufficient to identify it uniquely)
Any commit label such as a branch or tag name
The label HEAD always refers to the currently checked-out commit (usually the head of the branch, unless you used git checkout to jump back in history to an old commit)
Any of the above plus ~ to refer to previous commits. For example, HEAD~ refers to one commit before HEAD and HEAD~5 refers to five commits before HEAD.

提交为检查点
In Subversion and other older, centralized version control systems, commits are permanent - once you make them, they are there on the server for everyone to see. In Git, your commits are local and you can combine, rearrange, and edit them before pushing them to the server. This gives you more flexibility and lets you use commits as checkpoints. Commit early and commit often.

编辑以前的提交

git commit --amend

allows you to modify the previous commit. The contents of the index will be applied to it, allowing you to add more files or changes you forgot to put in. You can also use it to edit the commit message, if you would like.

插入、从新排序和更改历史记录

git rebase -i <commit>

will bring up a list of all commits between and the present, including HEAD but excluding . This command allows you rewrite history. To the left of each commit, a command is specified. Your options are as follows:
The "pick" command (the default) uses that commit in the rewritten history.
The "reword" command lets you change a commit message without changing the commit's contents.
The "edit" command will cause Git to pause during the history rewrite at this commit. You can then modify it with git commit --amend or insert new commits.
The "squash" command will cause a commit to be folded into the previous one. You will be prompted to enter a message for the combined commit.
The "fixup" command works like squash, but discards the message of the commit being squashed instead of prompting for a new message.
Commits can be erased from history by deleting them from the list of commits
Commits can be re-ordered by re-ordering them in the list. When you are done modifying the list, Git will prompt you to resolve any resulting merge problems (after doing so, continue rebasing with git rebase --continue)
When you are done modifying the list, Git will perform the desired actions. If Git stops at a commit (due to merge conflicts caused by re-ordering the commits or due to the "edit" command), use git rebase --continue to resume. You can always back out of the rebase operation with git rebase --abort.
Warning: Only use git rebase -i on local commits that have not yet been pushed to anybody else. Modifying commits that are on the central server will cause merge problems for obvious reasons.
Note: Vim makes these rebase operations very simple since lines can be cut and pasted with few keystrokes.

Git提示符
The Git package comes with a prompt script. To enable the prompt addition you will need to source the git-prompt.sh script and add $(__git_ps1 " (%s)") to you PS1 variable.
Copy /usr/share/git/completion/git-prompt.sh to your home directory (e.g. ~/.git-prompt.sh).
Add the following line to your .bashrc/.zshrc:
source ~/.git-prompt.sh
For Bash:

PS1='[\u@\h \W$(__git_ps1 " (%s)")]\$ '

Note: For information about coloring your bash prompt see Color_Bash_Prompt
For zsh:

PS1='[%n@%m %c$(__git_ps1 " (%s)")]\$ '

The %s is replaced by the current branch name. The git information is displayed only if you are navigating in a git repository. You can enable extra information by setting and exporting certain variables to a non-empty value as shown in the following table:

TODO: 表格格式化

Variable    Information
GIT_PS1_SHOWDIRTYSTATE  * for unstaged and + for staged changes
GIT_PS1_SHOWSTASHSTATE  $ if something is stashed
GIT_PS1_SHOWUNTRACKEDFILES  % if there are untracked files

传输协议

智能HTTP

Since version 1.6.6 git is able to use the HTTP(S) protocol as efficiently as SSH or Git by utilizing the git-http-backend. Furthermore it is not only possible to clone or pull from repositories, but also to push into repositories over HTTP(S).
The setup for this is rather simple as all you need to have installed is the Apache web server (with mod_cgi, mod_alias, and mod_env enabled) and of course, git:

Once you have your basic setup up and running, add the following to your Apache's config usually located at /etc/httpd/conf/httpd.conf:

<Directory "/usr/lib/git-core*">
    Order allow,deny
    Allow from all
</Directory>

SetEnv GIT_PROJECT_ROOT /srv/git
SetEnv GIT_HTTP_EXPORT_ALL
ScriptAlias /git/ /usr/lib/git-core/git-http-backend/

The above example config assumes that your git repositories are located at /srv/git and that you want to access them via something like http(s)://your_address.tld/git/your_repo.git. Feel free to customize this to your needs.
Note: Of course you have to make sure that your Apache can read and write (if you want to enable push access) on your git repositories.
For more detailed documentation, visit the following links:
http://progit.org/2010/03/04/smart-http.html
https://www.kernel.org/pub/software/scm/git/docs/v1.7.10.1/git-http-backend.html

Git SSH
You first need to have a public SSH key. For that follow the guide at Using SSH Keys. To set up SSH itself, you need to follow the SSH guide. This assumes you have a public SSH key now and that your SSH is working. Open your SSH key in your favorite editor (default public key name is ~/.ssh/id_rsa.pub), and copy its content (Ctrl+c). Now go to your user where you have made your Git repository, since we now need to allow that SSH key to log in on that user to access the Git repository. Open ~/.ssh/authorized_keys in your favorite editor, and paste the contents of id_rsa.pub in it. Be sure it is all on one line! That is important! It should look somewhat like this:
Warning: Do not copy the line below! It is an example! It will not work if you use that line!

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQCboOH6AotCh4OcwJgsB4AtXzDo9Gzhl+BAHuEvnDRHNSYIURqGN4CrP+b5Bx/iLrRFOBv58TcZz1jyJ2PaGwT74kvVOe9JCCdgw4nSMBV44cy+6cTJiv6f1tw8pHRS2H6nHC9SCSAWkMX4rpiSQ0wkhjug+GtBWOXDaotIzrFwLw== username@hostname

Now you can checkout your Git repository this way (change where needed. Here it is using the git username and localhost):
git clone git@localhost:my_repository.git
You should now get an SSH yes/no question. Type yes followed by Enter. Then you should have your repository checked out. Because this is with SSH, you also do have commit rights now. For that look at Git and Super Quick Git Guide.

特定非标准端口
Connecting on a port other than 22 can be configured on a per-host basis in /etc/ssh/ssh_config or ~/.ssh/config. To set up ports for a repository, specify the path in .git/config using the port number N and the absolute path /PATH/TO/REPO:

ssh://user@example.org:N/PATH/TO/REPO

Typically the repository resides in the home directory of the user which allows you to use tilde-expansion. Thus to connect on port N=443,

url = git@example.org:repo.git

becomes:

url = ssh://git@example.org:443/~git/repo.git

Git守护进程
Note: The git daemon only allows read access. For write access see #Git SSH.
This will allow URLs like "git clone git://localhost/my_repository.git".
Edit the configuration file for git-daemon /etc/conf.d/git-daemon.conf (GIT_REPO is a place with your git projects), then start git-daemon with root privileges:

# systemctl start git-daemon@

To run the git-daemon every time at boot, enable the service:

# systemctl enable git-daemon@

Clients can now simply use:

git clone git://localhost/my_repository.git

Git版本库权限 To restrict read/write access, you can simply use Unix rights, see http://sitaramc.github.com/gitolite/doc/overkill.html For a fine-grained rights access, see gitolite and gitosis