Version Control, Revision Control

Software Configuration

Management

Version Control

During software development it is inevitable

•To be able to recreate any earlier internally or externally released version

of the software product

•Giving the possibility to turn back in case of development dead-end

•Control changes of software source code continuously

•Identify faults and problematic code parts more easily

SCM

• Version Control is part of Software Configuration Management (SCM), which activity keeps coherent software versions together.

• Internal release: coherent software build for verification (testing)

• External release: coherent software build for external, customer use

• SCM usually refers more than VC, also means product component registration, 3PP related activities, may be supply activities as well. It depends on the actual project (company) setup.

Traditional vs. Distributed

Traditional• server oriented• clients works online or make snapshots locally

Distributed• Peer to peer approach• All local machines have the whole (complete) repository• Local repos sync amongst each other• Only working copies exist (every cloned repo is a working copy)

• No canonical, reference copy of the codebase exists by default; only working copies. = No special authority for any repository

• Common operations (such as commits, viewing history, and reverting changes) are fast, because there is no need to communicate with a central server.

• Communication is only necessary when sharing changes among other peers.• Each working copy effectively functions as a remote backup of the codebase and of

its change-history, protecting against data loss.• Disadvantages

• initial cloning can be terribly long• missing reserved checkout is a problem in case non-mergable binary files

Traditional vs. Modern

• Traditional• items (files) are version

controlled and every file can be checked in separately

• it does not guarantee that system is continuously coherent

• Consider changes together• all modified files are checked in

as one step and one identifier (generally a hash) identifies the whole system actual state

• cherry-picking is possible but not a proposed way

• Traditional• prevent parallel development by

file locking (reserved checkout)• or by parallel development tracks

and integrate at the end

• Modern ones• reserved checkout is not usual• frequent merges are common

and forced by the tool

Version Control Implementations

• (IBM Rational) Clearcase• Git• CVS, Subversion• Mercurial• Fossil• Internal

• Wiki pages• Google Docs• Microsoft Office

Clearcase Naming Conventions and Branching

• This is a visual representation of versions of one item, “above” this, there is a file and folder view as in any normal file structure

• The root is “main” branch• Versions are numbered and • Branches are named• Labels indicating releases (see

next slide)

• Red arrows are merges• “Config spec” tells what

you see from the system

Clearcase Complex Branching

Branching in general (DVCS)

• This is a visual representation of versions of items or the whole repo (in case of distributed systems), “under” this, there is a file and folder view as in any normal file structure

• The root is usually called “trunk”• Red arrows are merges

Fossil and branching

• Hashes vs. incremental numbers• Fig. 1: an ideal world• Directed acyclic graphs (DAGs) but

everyday usage tree is enough• “directed acyclic graph (DAG), is a

directed graph with no directed cycles.” Link

• Forks (fossil tries to prevent forks)• Warns to do fossil update to fetch

the other already committed version

• Git supports forks quite much• Fig. 2-3

• Branches• Deliberate forking for example

because of two teams using different version of the SW

• Fig. 4• Merge back to “main” – dashed

arrows

Fossil and branching

• A tag is a name that is attached to a check-in.

• A property is a name/value pair. • The branch tag tells (by its

value) what branch the check-in is a member of.

• The default branch is called "trunk.“

• Link to read in details.

Fossil and branching

• Branch• A branch is a set of check-ins with the

same value for their "branch" property.

• Leaf• A leaf is a check-in with no children in

the same branch.

• Closed Leaf• A closed leaf is any leaf with the closed

tag. These leaves are intended to never be extended with descendants and hence are omitted from lists of leaves in the command-line and web interface.

• Open Leaf• A open leaf is a leaf that is not closed.

• Fork• A fork is when a check-in has two or

more direct (non-merge) children in the same branch.

• Branch Point (branching out)• A branch point occurs when a check-in

has two or more direct (non-merge) children in different branches. A branch point is similar to a fork, except that the children are in different branches.

Concepts

Concepts•Atomic operations•File locking•Version merging•Baselines, labels and tags

Concepts and Branching Strategies

Concepts•Store everything under version control which you want to keep•Not only source code files, but

• configuration files• install scripts• documentation• released packages

•Nothing to delete, add a new version

• if an item is not needed remove from version control but it means you have all earlier version in repository

Branching strategies in a SW Development Project•one track•one main, one development•feature branches•private branches•fossil branching

Terms need to know and understand•repository•check out

• reserved• unreserved

•check in•merge

CEA 2/EEA 15 Planned RELEASE BRANCHING

2.0 PRA Final build

R1A

2.0 ICP1 Preship

2.0 EP1 R1A/1

2.0 ICP1 R1B

P1B : R1B P1A : R1A

R1A : R1B R1B : R1A

15.0 ICP1 R2B

15.1 PRA Final build

R3A

15.0 PRA Final build

R2A

15.0 Preship#1 / #2

15.0 ICP2 R2C

. . .

. . .

2.0 ICP2 R1C

15.1 ICP1 R3B

15.1 ICP2 R3C

Corrected product’s R-State

Faulty product’s R-State on this specific branch

<

<

<

<

>

>>

New productnumber created for EEA 15

CXP 902 …/3 CXP 902 …/3

CXP 902 …/2 CXP 902 …/3

Fossil commands

• new/init• clone• open

• add• rm• checkout (quite different than

usual, do not use at first)• changes• revert• diff• gdiff• commit/checkin

• pull/push/sync• update (your local tree)• merge• undo• server• ui• close• extras• Autosync

• http://www.fossil-scm.org/fossil/doc/trunk/www/quickstart.wiki

• http://fossil-scm.org/xfer/help