Pro Git

第一章 起步

Git config

级别

文件位置

flag

系统级

/etc/gitconfig

--system

用户级

~/.gitconfig

--global

repo

.git/config

--local (default)

# set user name and email
git config user.name "David Feng"
git config user.email davidfeng@abc.com
# see the config
git config --list
# get help
git help config

Note: env variables such as GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL will override the user name and email in config.

第二章 Git基础

查看修改

git status

git diff: difference between working directory vs. staged files.

git diff --staged: staged files vs. committed files.

Commit

git commit -a -m "msg": commit all tracking files, skip staging (no need for git add)

移除和移动文件

git rm file git mv file1 file2: same as three commands - mv file1 file2; git rm file1; git add file2

---- In progress ----

Git log

show git diff of the commits

git log -p 限制输出长度 --since/after/until/before only show changes for : git log path

only show commits that add/delete a function or variable: git log -S function_name

撤销操作

replace the previous commit: git commit —amend discard changes for a file: git checkout —filename

Remote Repo

List all of them: git remote add a remote repo: git remote add alias url fetch (not merged yet): git fetch <remote name> push: git push origin master show all branches of remote repo and their relations with local branches: git remote show origin

Git alias

git config --global alias.co checkout

then git co => git checkout

第三章 Git分支

Branches are pointer to commit objects HEAD: an alias for current branch

Create a new branch and switch to it

git checkout -b newbranch => 1. git branch newbranch (create a new branch); 2. git co newbranch

Merge a new branch

git checkout master git merge js1234

Branch Dev workflow

multiple branches.

More stable, less feature master/next/feature less stable, more feature prod_an/mass-release

Remote Branches

fetch: git fetch origin push: git push origin js1234

show local branches and tracked remote branches: git branch -vv

show all local branches and last commits: git branch -v

pull: git pull (fetch + merge)

Rebase

Calculate changes in commits in the new branch; discard those commits; generate new commits containing those changes on top of the new based branch. Basically rewrite commit history so no branch happend. Everything is linear.

  1. git checkout feature

  2. git rebase master

  3. git checkout master

  4. git merge feature (fast forward)

shortcut: git rebase [new base branch] [topic branch]

A more advanced example:

master branch out server. On server, branch out client. How can I merge client into master, but don’t merge server?

git rebase --onto master server client

=> get client branch, find client specific change (after the common ancestor of client and server), add those changes to master. Don't rebase branches that have copies outside of your local repo. A common fix: git pull --rebase

Merge vs. Rebase

Merge: commit history should show what happened. We should not change it.

Rebase: commit history is a story. No one wants to read the first draft of your novel.

第四章 Git on Server

There are several protocols, each with pros and cons: local, http, ssh, git.

bare repo: no working directory, just .git folder.

第五章 分布式Git

git diff -- check: run to show common errors such as whitespaces at the end of line. Commit message: first line: summary , empty line, followed by explanation. git log --no-merge issue..origin/master only show commits in origin/master but not in issue git cherry-pick hash: pull one commit into current branch (by creating a new commit) On master, pick one of the commits on feature branch

第六章 GitHub

第七章 Git工具(高级命令)

Parent commit

Git show hash HEAD~ HEAD~2 (HEAD^2 is for merge commit, which has two parents) Or HEAD~~^

Commit intervals

Git log master..feature Log commits that are in feature but not master Git log origin/master..HEAD Git log refA refB ^refC (show commits that are in refA, in refB, not in refC) Git log --left-right master...feature (show commits in either branch but not both)

Remove untracked files

Git clean -n dryrun -f force -d also removes empty directory

Search string

Git log -S string Show commits that adds or modifies the string

Git log -L :function:file.c Git will get the lines of the function and search for the change history of those lines

Rewrite history

just like rebase, don't do it if you already pushed. Modify the last commit message: Git commit --amend

Reset and checkout

reset: move where HEAD points to. checkout: change HEAD.

i.e. if we are on master, (HEAD is on master), and we do git reset hash, then master/HEAD will be on that hash.

the model of three trees: HEAD, index/staging, working directory HEAD is last commit, the parent of next commit.

Git reset hash: try to move Head to that commit

Git reset --soft HEAD~ Move head to its parent. No change to index and working directory Now we can modify staging Just revert HEAD (revert git commit)

--mixed default behavior revert head and staging (revert git add) --hard revert all three, including working directory Git reset file.txt (default hash is HEAD) Effectively unadd file.txt Git reset hash file.txt Git reset --soft HEAD~2 Reset HEAD but no changes in index and working directory So for commit will effectively squash commits Then push will only push reachable history

Checkout:

Gco [branch] => git reset --hard [branch] but safer. Will stop if working directory is not clean. Checkout: move HEAD to another branch Reset: move HEAD with the current branch Checkout file.txt: reset --hard

Advanced Merge

Git merge --abort abort the merge Git checkout --conflict=diff3 hello.rb shows ours, theirs, and the base Ours option (just use our code, discard their changes. Useful when we know that we should always use one side’s code, i.e. generated file) vs. ours strategy (lie to git, let it think we merged but no code is changed)

Debug

Git blame -L 12,20 file.txt ^hash means it's the first added line and never modified afterwards -C also get lines that added from other files Git bisect can help you find out which commit introduced the error

Submodules

To include other repo (may be some dependencies) in your repo you want to distribute within your software

Git bundle

Bundle git data into an binary so that we can email it.

Git replace

Use an object (commit) to replace another object. Can be used to create a shorter commit history.

第八章 配置Git

help.autocorrect 50

if you input a command that does not exist, git will guess. If there is only one candidate, git will run it after 5s.

git attributes

apply certain configs in certain paths

git hooks

any script that will be run at certain times, e.g. before commits.

第九章 Git与其他VCS

第十章 Git内部原理

Git对象

blob对象 => 文件的不同版本

树对象 => 目录项

commit对象 => 指明顶层树对象和父提交对象的提交对象

Git引用

branch: a pointer to the head of a series of commits. HEAD: a pointer to the current branch Commits: pointer to tree. Tag object: pointer to commit. A branch that can't move Search files in path find .git/objects -type f

loose: store multiple copies of slightly different versions of a file

pack: Store the latest version of files and delta to previous versions git gc manual pack, remove object that are not connected with any commits.

How to recover from hard reset

method1:

git reflog or git log -g

shows the historical value of HEAD. to get lost commit hash

git branch newBranch hash method2: (big gun) git fsck --full show dangling objects

---- 整理至此 ---- git prune Git bash utility! Auto complete? Prompt??

常用命令

Git short log

整理git reset 整理笔记

low level commands: plumbing. high level: porcelain git init projectname Git对象 Save object to git git hash-object -w --stdin # --stdin: use stdin as source. default: at the end, put the source (file)’s path. -w: save the object. it produces a 40-character hash. first 2 are directory name, last 38 are filename. Retrieve data: git cat-file -p HASH # -p: pretty-print object's content git cat-file -t HASH # give the object’s type: blob 数据对象 树对象 (类似于目录) git cat-file -p master^{tree} # master分支上最新的提交所指向的树对象。 创建树对象:git 根据暂存区状态创建并记录一个对应的树对象。1. 创建暂存区。2. update-index. git update-index --add --cacheinfo 100644 \ 83baae61804e65cc73a7201a7252750c76066a30 test.txt # --add 将该文件加入暂存区 --cacheinfo要添加的文件位于git数据库中,而不是当前目录下,文件模式100644普通文件,100755可执行文件,120000符号链接。 git write-tree #将暂存区内容写入一个树对象 不需要-w,如果某个树对象此前不存在,会自动创建 git read-tree --prefix=bak HASH: 可以把HASH代表的树对象读入暂存区。若基于该暂存区创建树对象 git write-tree 再基于此树对象创建一个工作目录,则这个工作目录会包含bak子目录 提交对象commit object 创建提交对象: 内容:一个树对象,注释,父提交对象 echo ‘first commit’ | git commit-tree TREEHASH echo ‘second commit’ | git commit-tree TREEHASH [ -p PARENT COMMIT HASH] git log --stat COMMITHASH git add & git commit的底层命令:将被改写的文件保存为数据对象,更新暂存区,记录树对象,最后创建提交对象(明确顶层树对象和父提交对象)。 Git引用Refs commit的代号 echo COMMITHASH > .git/refs/heads/master 编辑引用文件的推荐方法:Do not edit ref file. Use update-ref instead. git update-ref refs/heads/master NEWCOMMITHASH git branch (branchname)的底层命令:update-ref HEAD: 符号引用。不像普通引用一样包含最新commit对象的SHA-1.它是一个指向其他引用的指针。 git checkout的底层命令:更新.git/HEAD git commit: 创建commit object, 并用HEAD文件中那个引用指向的SHA-1设置成父commit object. 编辑HEAD文件的推荐方法:symbolic-ref git symbolic-ref HEAD #读 git symbolic-ref HEAD refs/heads/test #写 ToDo: 标签引用

git prune ????

git gc ????

Git config --list show me this: what do they mean?

credential.helper=osxkeychain

alias.a=add

alias.aa=add --all :/

alias.alias=config --get-regexp ^alias\.

alias.b=branch

alias.ci=commit

alias.co=checkout

alias.d=diff --ignore-space-change

alias.l=log --pretty=format:"%C(green)%h%C(reset) %C(blue)%ad%C(reset) %s%C(yellow)%d%C(reset) %C(blue)[%an]%C(reset)" --graph --date=short

alias.s=status

alias.r=remote

color.ui=true

core.excludesfile=~/.gitignore

push.default=simple

user.name=davidfeng88

user.email=david.feng.ge@gmail.com

core.repositoryformatversion=0

core.filemode=true

core.bare=false

core.logallrefupdates=true

core.ignorecase=false

core.precomposeunicode=true

remote.origin.url=https://github.com/davidfeng88/bara.git

remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*

branch.master.remote=origin

branch.master.merge=refs/heads/master

user.name=davidfeng88

remote.heroku.url=https://git.heroku.com/bara1.git

remote.heroku.fetch=+refs/heads/*:refs/remotes/heroku/*