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This article introduces the relevant knowledge of "basic concepts and core commands of Git". Many people will encounter such a dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Course outline:

Overview of GIT system

GIT core commands use the

Basic principle of GIT

I. Overview of GIT system

Questions:

What tools does your company use to manage code versions? SVN 、 CVS 、 GIT

What's the difference between GIT and SVN?

The main differences between GIT and svn:

Storage methods are different.

Use it in a different way

Management mode is different

1. Difference in storage mode

GIT stores content as metadata, similar to KLV database, while SVN stores content by file (the new version of svn has been changed to metadata storage)

Demo git stored procedure demo

Cd .git / objects/df/

Git cat-file-p df70460b4b4aece5915caf5c68d12f560a9fe3e4

Echo 'version1' > text.txt

Git hash-object-w text.txt

2. Differences in ways of use

To push files locally to a remote service, SVN only needs commint, while GIT needs add, commint and push.

Basic use process of SVN

Basic use process of Git

3. Differences in version management modes.

Git is a distributed version management system, while SVN is a remote centralized management system.

Centralized type

Distributed system

Second, the use of GIT core commands

Main contents:

Git client installation configuration

Overall understanding of the basic use of GIT

Branch management

Label management

Remote warehouse configuration

1. Install git client installation

Official client: httpsd://git-scm.com/downloads

Other clients: https://tortoisegit.org/download/

2. Recognize the basic use of GIT

Git project creation and cloning

File submission and push

Complete simulation of the process of adding from a project to push

Create a project

Initialize the git repository

Submit a document

Remote association

Push to remote warehouse

Initialize the GIT repository locally:

# Clone to local based on remote warehouse

Git clone

# initialize the current directory to the git local repository

Git init

Create a project based on a mvn template

Mvn archetype:generate

Add locally

# add the specified file to the staging area

Git add

# add the specified directory to the temporary storage area

Git add

# add all

Git add-A

# remove the specified directory and subdirectories from the scratch area

Git rm-cached target-r

# add omitted configuration file .gitignore

Local submission

# submit to the local warehouse

Git commit file-m 'submit comments'

# Quick submission to local warehouse

Git commit-am 'add and submit'

3. Branch management

# View the current branch

Git branch [- avv]

# create a new branch based on current branch

Git branch

# create a new branch based on submission

Git branch

$git branch-d {dev}

# switch branches

Git checkout

# merge branches

Git merge

# resolve conflicts. If automatic merge fails due to conflicts, status is in mergeing status.

# need to manually modify and resubmit (commit)

4. Remote warehouse management

# View remote configuration

Git remote [- v]

# add remote address

Git remote add origin http:xxx.xxx

# Delete remote address

Git remote remove origin

# upload a new branch to remote

Git push-set-upstream origin master

# associate the local branch with the remote

Git branch-track-set-upstream-to=origin/test test

5. Tag management

# View current

Git tag

# create a branch

Git tag

# Delete branches

Git tag-d

6. Log management

# View all submission logs under the current branch

Git log

# View all submission logs under the current branch

Git log {branch}

# display logs on a single line

Git log-oneline

# compare the differences between the two versions

Git log master..experiment

# display the submission merge network as a chart

Git log-- pretty=format:'%h% s'--graph

Third, the underlying principle of git

GIT storage object

GIT tree object

GIT submit object

GIT reference

1. GIT storage object (hashMap)

Git is a content addressable file system, its core part is a simple key-value database (key-value data store), you can insert anything into the database, it will return a hash key to retrieve the value.

# insert data into git key-value library

Echo 'luban is good man' | git hash-object-w-- stdin

79362d07cf264f8078b489a47132afbc73f87b9a

# get the specified content based on key

Git cat-file-p 79362d07cf264f8078b489a47132afbc73f87b9a

Based on this function, Git saves the contents of the version of each file in the database, and uses one of the keys to retrieve and replace the date when the version is to be rolled back.

Simulate and demonstrate the process of writing and rollback of git version

# find all git targets

Find .git / objects/-type f

# write to version 1

Echo 'version1' > README.MF; git hash-object-w README.MF

# write to version 2

Echo 'version2' > README.MF; git hash-object-w README.MF

# write to version 3

Echo 'version3' > README.MF; git hash-object-w README.MF

# rollback the specified version

Git cat-file-p c11e96db44f7f3bc4c608aa7d7cd9ba4ab25066e > README.MF

So our common git add is actually inserting the modified content into the key-value library. When we execute git add README.MF, it is equivalent to executing git hash-object-w README.MF to write the file to the database.

We have solved the storage problem, but it can only store the content and not the file name. How do you know which content corresponds to which file if you want to roll back? The next thing to talk about is the tree object, which solves the problem of file name storage.

2. GIT tree object

Tree object solves the problem of file name, its purpose is to organize multiple file names together, which contains multiple file names and their corresponding references to Key and other tree objects, which can be understood as folders in the operating system, and a folder contains multiple files and other folders.

Each branch is associated with a tree object that stores all the file names and corresponding key under the current branch.

You can view it with the following command

# View the branch tree

Git cat-file-p mastery ^ {tree}

3. Git submission object

A submission is a snapshot of the current version, which is saved through the submission object, which stores the following contents: a top-level tree object, the last submitted object, the submitter's user name and mailbox, the submission timestamp, and the submission comment.

$git cat-file-p b2395925b5f1c12bf8cb9602f05fc8d580311836

Tree 002adb8152f7cd49f400a0480ef2d4c09b060c07

Parent 8be903f5e1046b851117a21cdc3c80bdcaf97570

Author tommy 1532959457 + 0800

Committer tommy 1532959457 + 0800

From the above knowledge, we can infer that a total of three objects are generated from the process of modifying a file to submitting:

A content object stores the contents of the file

A tree object = > stores the key of the file name and content object

A submit object = > stores the key of the tree object and submits comments.

Presentation file submission process

4. GIT citation

When we execute git branch {branchName}, we create a branch, which essentially creates a reference file based on the specified submission in git and saves it under .git\ refs\ heads\.

Demonstrate the creation of a branch

Git branch dev

Cat.git\ refs\ heads\ dev

There are three types of references to git:

Branch reference

Remote branch reference

Label referenc

# query to compare two versions

Git log master..experiment

# version submission History Network

Git log-- pretty=format:'%h% s'--graph

# View the branch tree

Git cat-file-p mastery ^ {tree}

This is the end of the introduction to the basic concepts and core commands of Git. Thank you for your reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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