Svn(subversion) is a version management tool that has emerged in recent years, and it is the successor of cvs. At present, most open source software uses svn as code version management software.

workflow

The workflow of centralized management is as follows:

The core of centralized code management is the server. Before starting a new day's work, all developers must get the code from the server, then develop it, and finally resolve the conflict and submit it. All version information is put on the server. Without servers, developers can basically be said to be unable to work. Here is an example:

Start a new day's work:

1. Download the latest code of the project team from the server.

2. Enter your own branch, work, and submit the code to your own branch of the server every hour (many people have this habit. Because sometimes you have to modify the code, and finally you want to return to the previous hour's version, or see which code you modified in the previous hour, you need to do this).

It's almost time to get off work. Merge your own branch into the main branch of the server, and a day's work will be completed and reflected on the server.

This is a classic svn workflow. From the process point of view, there are many shortcomings, but there are also advantages.

disadvantaged

1, the server is under too much pressure and the database capacity explodes.

2. If you can't connect to the server, you basically can't work. See the second step above. If the server is not connected, you can't submit, restore, compare and so on.

3, not suitable for open source development (a large number of developers, but Google app engine uses svn). The general centralized management has a very clear authority management mechanism (such as branch access restrictions), which can realize hierarchical management, thus solving the problem of a large number of developers.

superiority

1, easy to manage, clear in logic, in line with the thinking habits of ordinary people.

2, easy to manage, and the centralized server can ensure security.

3. The code consistency is very high.

4. Suitable for projects with few developers.

5. Most university textbooks of software configuration management use svn and vss. [3]

Edit this paragraph security.

SVN integrates "organic" and "seamless" safety products from a higher level of system and control.

SVN is a secure virtual network system, which distributes the information security functions of the whole system in different subsystems in a balanced and reasonable way, so that the functions of each subsystem can be fully exerted and the subsystems complement each other. The overall performance of the system is greater than the sum of the functions of each subsystem, and the problem of "Kannikin's Law" is solved by the principle of balance and complementarity.

SVN can achieve comprehensive security at all endpoints of the network spanning Internet, Intranet, Extranet and Extranet, and can also provide an information management mechanism based on enterprise policies to make full and effective use of limited bandwidth. By providing secure Internet-based connections for the company's internal network, remote and mobile users, branches and partners, SVN can meet the requirements of various enterprise VPN. Therefore, we can regard SVN as an integrated Internet security solution based on enterprise strategy, which integrates VPN, firewall and information management software. In such a network system, all Internet servers and clients are secure, and there is an information management mechanism to dynamically analyze and meet the specific bandwidth requirements of customers through this external network environment. SVN provides security services for network-based e-commerce applications, including:

Conduct comprehensive safety certification for various applications;

Support multiple authentication and PKI；;

Provide users with powerful and transparent communication encryption;

Centralized user-oriented security policy management;

Unified communication across internet, intranet and extranet.

Edit this paragraph schema

VPN gateway with firewall is a gateway product that closely combines firewall and VPN technology.

SVN security remote client software package, a powerful VPN client software, supports desktop users, remote users and mobile users, has the function of personal firewall, and carries out centralized management and security authentication for VPN users;

SVN certificate management module, SVN complete PKI solution, integrated with perfect CA and LDAP directory server technology;

SVN hardware encryption card can realize various powerful algorithms through hardware technology to improve the speed and performance of VPN.

SVN intelligent bandwidth management module, a bandwidth management solution based on enterprise strategy, can intelligently manage limited bandwidth resources and ensure the reliable performance of VPN used in important enterprise applications;

SVN redundancy management module, through redundant gateway cluster and SVN redundancy module in firewall VPN, seamlessly switches VPN and firewall applications that perform important tasks when they fail.

Automatic address translation module is a solution to automatically manage IP addresses and naming. By providing tracking and centralized management of IP address services, it ensures reliable control of address allocation and improves TCP/IP management efficiency.

SVN security server software package, a VPN gateway software specially designed to protect the security of a single application server, can protect sensitive servers from attacks and unauthorized access, enable clients to establish security authentication with servers, and support the connection of exchanging encrypted data;

SVN security client software package integrates firewall based on state detection and VPN client software based on IPSec on the client machine, which enhances the security of the client machine by providing centralized personal firewall and security authentication for all enterprise VPN users. Compared with the functions of SVN security remote client software, it enhances the security functions of the client, such as access control and security initialization control.

Edit the development history of this paragraph.

At the beginning of 2000, the developer wanted to write a free software substitute for CVS, which kept the basic idea of CVS, but did not have its mistakes and limitations, and kept its basic features but removed its bugs and bad features.

In February 2000, they contacted the open source development of CVS.

With CVS) (Coriolis, 1999).

Vogel asked him if he would like to play a role in this new project. Coincidentally, Karl has discussed a new version control system with his friend Jim Blandy.

Design of the system. 1995, they founded Cyclic.

Software, a software company that provides commercial support for CVS. Although they run commercial services, they still use CVS in their work every day. The frustration of using CVS made Jim serious.

Thinking about a better data management method not only determines the name "Subversion", but also completes the basic design of Subversion archive.

When CollabNet called, Karl immediately agreed to join the project, and Jim got his employer RedHat Software to agree to let him work irregularly in the project. CollabNet hired Karl and Ben Collins-Sussman and started detailed design work in May. With the help of many ideas of Brian Behlendorf, Jason Robbins and Greg Stein (a freelance programmer who was active in the WebDAV/DeltaV specification process at that time), Subversion quickly attracted the attention of the active developer community. It found and welcomed many members who also suffered setbacks on CVS to do something for this project.

Subversion's original design team set several simple goals. It must be functionally replaceable with CVS, that is,

Everything CVS can do, it can certainly do. While correcting the most obvious defects, we should maintain the same development model. In addition, subversion should be related to

CVS is very similar, and any CVS user can get started quickly with a little effort.

After fourteen months of coding, Subversion began to realize "self-management" on August 3 1 2006. In other words, developers no longer use CVS to manage Subversion's code, but Subversion itself.

Subversion was accepted by Apache incubator in June 2009 +2009 10.

20 1 1 1 has officially become a top-level project of Apache software foundation, so it is Apache Subversion. [4]

At present, the chairman of Apache Subversion is Greg Stein, and the project leader is Wandisco. [4]

Advantages and disadvantages of editing this paragraph

All the documents show that SVN can replace CVS, and the problems and shortcomings of SVN are hidden. Unfortunately, we don't think SVN is a substitute for CVS, although many defects have been modified. What's more, it even brought people back to CVS.

The comparison between CVS and SVN is similar to that between C++ and Java. Obviously, CVS and SVN are much more powerful than SourceSafe, just as C++ and Java are more powerful than Basic.

A lot. CVS represents almost all the functions of a code control system, although sometimes its implementation is not very convenient. SVN fixes and adds some functions that CVS doesn't have. For example, create flags and branches.

Suspicious, when you edit the file, no one will notice. SVN is not a substitute for CVS, but a different system, similar to CVS. It has some unique functions, enough to adopt it.

Reason. These features make him more suitable for development environment, such as PowerBuilder. Below you can find their relative advantages and disadvantages.

1 storage type format

CVS is a version control system based on RCS file. Each CVS file is just an ordinary file, plus some extra information. These files will simply repeat the tree structure of local files. Therefore, there is no need to worry about any data loss, and the RCS file can be modified manually if necessary.

SVN is based on a relational database (BerkleyDB) or a series of binary files (FS_FS). On the one hand, it solves many problems (such as reading and writing files in parallel) and adds many new functions (such as transaction characteristics of runtime). )。 On the other hand, however, data storage becomes opaque.

2 speed

CVS is slow.

Generally speaking, SVN is indeed much faster than CVS due to different architecture implementations. On the network, it only transmits a little information, and supports more functions in offline mode. But it also comes at a price. The price of speed is huge storage (completely backing up all working files).

Three signs &; branch

SVN used flags and branches and abandoned the other three things. In fact, this means that they replace this concept with copying files or directories in the archive.

Save the log. In this way, flag creation and branch creation are just file copying in the warehouse. For branches: branches are just a separate directory in the warehouse, unlike in the early days.

Yao staggered for a moment. For tagging: It is no longer possible to tag code. To some extent, SVN's complete file number makes up for this defect. SVN's entire warehouse has a version number, but a single file does not.

4 yuan data

CVS only allows storing files.

SVN allows a file to have any number of nameable attributes, and its function is very complete.

Five file types

CVS was originally designed for text file storage. Therefore, other file types (binary, Unicode) are rarely supported. If necessary, there should be other information and adjust the client-server side.

SVN will care about all file types and doesn't need you to manually operate them.

6 rollback

CVS allows arbitrary rollback on any submitted version, although it takes some time (all files should be handled separately).

SVN does not allow rollback after submission. It is suggested to add the good version in the version library to the end to overwrite the damaged version. And the corrupted version will exist in the database anyway. (The rollback operation of SVN is actually a merge operation. )

7 affairs

The "zero or one" trading principle in CVS has not been realized at all. If several files are checked in (added to the server), it is likely that some files are completed and some files are not. As a hidden rule, manually correct these errors and check in the remaining files (not all files) one by one. Therefore, these files will be checked in in two stages. SVN does support the "zero or one" trading principle, which is one of the advantages of SVN.