1. INTRODUCTION TO
VERSION CONTROL

2. PURPOSE OF CURRENT
TRAINING
The basics
AND
Making first steps
2

3. CONTENTS
 What is version control
 History and evolution of version control
 Instruments and their classification
 Approaches
 Domain vocabulary
 What else you might want to know
3

4. WHAT IS VERSION CONTROL
 Place to store your source code
 Historical record of what you have done over time
 Approach which allows working together without
getting in each others' way (allows to collaborate
more effectively)
 Another “trendy” word combination
 Something that every software developer should
deal with
4

5. VERSION CONTROL. SYNONYMS
 Source code
management
 Source control
 Revision control
~SCM = Software
configuration Files Numbers
management
5
VERSION CONTROL

6. NOT VERSION CONTROL
Simple
Asset management documents, files, packages, tra
cked by filesystem
What exact versions of libraries
Dependency management are required
Music, pictures, drawings, book
Digital storage s
Installation managers, package
Package management dependencies
Installations management Installation is not a version
6

7. HISTORY AND EVOLUTION OF VERSION
CONTROL
 make utility (early 70's)  BitKeeper (1999)
 Bell labs paper describing the  GNU Arch (2001)
distributed
original diff algorithm (1972)  Monotone (2003)
 CDC update tool (early 70's.  darcs (2003)
contained revision control, change  git (2005)
sets, build management, file diffs)
 Mercurial (2005)
 SCCS source code control system
 Bazzar (2005)
(1972)
CCC version control system (1975)
proprietary
  ClearCase (1992)
 RCS revision control system (1980)  VSS (1994)
 patch utility (around 1988)  Perforce (1995)
 CVS Concurrent Version System  Vault (2002)
(1986), CVSNT (1998)  AccuRev (2002) 7
 Subversion (started in 1999)  TFS (2005)

8. VCS CLASSIFICATION
(BY REPOSITORY MODEL)
Centralized (client-server model)
• Subversion
• CVS
• VSS, TFS, Vault
• ClearCase
• AccuRev
Distributed
• Git
• Mercurial
• Bazzar
• Perforce
• BitKeeper 8

9. CONCURRENCY MODELS
combined
merge Release/lock
9

10. VCS CLASSIFICATION
(BY CONCURRENCY MODEL)
Merge
• CVS
• Git
• Mercurial
• Bazzar
Release/lock
• VSS
• TFS
• Vault
Combined
• Subversion
• AccuRev
• Perforce 10
• ClearCase

11. DISTRIBUTED VS CENTRALIZED.
Centralized Distributed
11

12. CENTRALIZED MODEL
12

13. DISTRIBUTED MODEL
13

14. DISTRIBUTED VS CENTRALIZED.
DIFFERENCES
Centralized Distributed
 Single repository  Multiple repositories
 Commit requires connection  Commit does not require
(no staging area). connection (due to staging area)
 Impossible to commit changes  Possible to commit changes to
to another user another user
 All history in one place  Impossible to get all history
 Reintegrating the branch might  Easier branches management
be a pain (especially reintegration)
 Considered to be not so fast as  Considered to be faster than
DVCS CVCS
 Easy access management  No access management
14
 Chosen for enterprise  Chosen for open source
development development

15. DISTRIBUTED MODEL.
WORKFLOW #1
15

16. DISTRIBUTED MODEL.
WORKFLOW #2
16

17. CONCURRENCY MODELS.
Lock-unlock Merge
 Everything is read-only  You can edit everything
 Need to edit?  Locally
1. Get lock  And commit changes later
2. Edit  Everything will be fine
3. Release lock  Unless somebody edited the
same files
 Don’t forget to release lock
 Otherwise you’ll need some luck
 Otherwise you screwed up
 You are:
 Others would not be able to 1. Lucky (source has been merged
edit locked files automatically)
2. Not lucky (conflict happened)
 There is a good thing though
 Conflicts require resolution
 You won’t need to merge  But it has nothing to do with 17
conflictology
 This is about merging manually

18. LOCK-MODIFY-UNLOCK
3. Sally tries to edit
1. GET LOCK
4. Locked!
2. Read
It’s impossible to edit
until Harry releases
the lock
5. Write
(save) 8. Read
6. RELEASE 7. GET LOCK
THE LOCK 18

19. ANTI VSS CAMPAIGN
19

20. COPY-MODIFY-MERGE (#1)
20

21. COPY-MODIFY-MERGE (#2)
21

22. PRACTICAL VERSION CONTROL
 What VCS to start with?  How to start working with
subversion?
 Subversion
 Get Subversion from official site
 Why? and install it
1. It’s most popular  Init new repository with
2. Enterprise chooses it svnadmin create command
3. EPAM has chosen it too  Create initial project structure
(/trunk, /tags/, /branches)
4. It has almost all what VCS
should have  Check created project out to
the directory with the source
5. It’s possible to use svn and git code
together if you wish  Add files with svn add
 Are you software developer? command
 Most likely you would need to  Commit files with svn commit
deal with subversion command 22

23. DOMAIN VOCABULARY.
START WORKING WITH VCS
checkin
add commit push
release lock
TO REPOSITORY
checkout
delete update,fetch pull
get lock
FROM REPOSITORY
23

24. DOMAIN VOCABULARY.
CVCS WORKFLOW EXAMPLE
WC (working copy) Repository
svn add
svn commit
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svn update

25. DOMAIN VOCABULARY.
DVCS WORKFLOW EXAMPLE
25

26. DOMAIN VOCABULARY.
RESPOSITORY INVARIANT OPERATIONS
add delete move
svn add, svn delete, svn rename, …
rename copy mkdir
 VCS is not able of flexible filesystem changes tracking
 It is preferably that instead of applying FS commands corresponding
VCS command be applied
 In other case files will be tracked by VCS as non-versioned or
missing.
 Subversion does not have specific commands for tags and branches 26
creation, svn copy is used instead.

27. DOMAIN VOCABULARY.
REPOSITORY LAYOUT
Repository
/
/trunk /branches /tags
Mainline Branches directory Tags directory
27

28. DOMAIN VOCABULARY.
CHANGELISTS
 You have bunch of committed  However, it has limitations
files 1. Changelists are applicable
 Which corresponds to the only to particular working
standalone feature copy
 You might want to track this 2. Changelists can be assigned
fileset only to files
 Then it’s time to use changelists 3. At most one changelist
 It is done by svn changelist assignment on one file
command  How could it be useful?
 It sets or unsets the changelist  It helps in logical
association of a particular organization of files being
working copy file committed
 You’ll be able to see changelists  For example in case, when
running svn status command one large feature should be
committed in several steps 28

29. DOMAIN VOCABULARY.
REVISIONS
Revisions
29
Working copy (WC)

30. DOMAIN VOCABULARY.
CHANGESET AND SNAPSHOT
changeset changeset changeset
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Tree snapshots

31. DOMAIN VOCABULARY.
PATCHING
svn diff > patchfile.patch
create patch
patch
apply patch
WC (working copy)
patch -p0 < patchfile.patch
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32. DOMAIN VOCABULARY.
METAINFO
working copy working copy
under subversion under git
metainfo
 WC under subversion has .svn folder in
each directory
 It allows tracking files status easily
 But has disadvantages
1. It takes too long to delete WC from FS
2. FTP upload is a headache
3. Web-application deployed together with
.svn folders is a security threat
4. It is easy to delete standalone .svn 32
folder and have some problems

33. WORKING COPY FILE STATUS
working revision
.svn
timestamp (last updated)
Unchanged, and current Unchanged, and out of date
14 18
= 14 ~
Locally changed, and current Locally changed, and out of date
33

34. DOMAIN VOCABULARY.
REVERT AND BLAME
 How to get rid of recent  Subversion tracks users
changes in WC? committing changes
 Make revert  This could be very helpful
 Why not update? sometimes
 Update does not override WC  Because you want to find
changes someone responsible
 Revert will discard all  One can find who changed
changes and return WC to specific lines
the working revision  By running svn blame
 Unless you have committed  It will show all user logins last
your changes edited specific line of code
 Revert will not help in that  Developer! Be aware
case.  Don’t commit buggy code
 But svn merge –rHEAD:N will  They’ll find you anyway 34

35. SUBVERSION VS CVS
Subversion CVS
 Commits are atomic  Commits are not atomic
 Renames and copies are  Renames and copies are
supported not supported
 Changesets messaging  Changes are file-specific
(per-commit message) (per-file commit message)
 Full permissions support  Permissions via hooks
 Difficulties with binary
files versioning  Easy binary files versioning 35

36. WORKING TOOLS
Subversion client
Command
line GUI
Subversion
TortoiseSVN IDE
server
embedded support Plugins
IntelliJ
Netbeans AnkhSVN Subclipse
IDEA
36

37. VERSION CONTROL FOR
NON-PROGRAMMERS
 There are version control tools even for designers:
Adobe version cue PixelNovel Timeline
 There is version control functionality embedded in:
37
Microsoft Word OpenOffice.org Writer

38. ISN'T VERSION CONTROL TOO
COMPLEX?
38

39. ISN'T VERSION CONTROL TOO
COMPLEX?
Basic working cycle
 You can avoid using version control  Update your working copy
 svn update
 But it can’t last long
 Make changes
 You will need to collaborate eventually  svn add
 It might be tricky sometimes  svn delete
 But you can avoid most problems  svn copy
 svn move
 Recommendations:
 Examine your changes
 Stick to basic working cycle  svn status
 Learn basic working cycle  svn diff
commands  svn revert
 Practice on sandbox project  Merge others' changes
 Read “Version control with  svn merge
subversion” book  svn resolved
 DVCSs have more steep learning  Commit your changes
curve anyway  svn commit
39

40. DOES SCM = VERSION CONTROL?
 No
 Version control is just the main SCM
process
 What is SCM then?
 There are several cumbersome definitions
 If you want it simple, it is just more broad
topic then just version control
 And it is one of the CMMI process areas
40

41. RECOMMENDED READING
1. Version control with Subversion By Ben Collins-
Sussman, Brian W. Fitzpatrick, C. Michael Pilato
48

42. RECOMMENDED READING
2. Version Control with Git by Jon Loeliger
49

43. RECOMMENDED READING
3. Pragmatic Version Control: Using Subversion, 2nd edition
by Mike Mason
50

44. USEFUL LINKS
1. http://svnbook.red-bean.com/ - official subversion
reference/book “Version Control with Subversion”
2. http://progit.org/ - book about git “Pro git”
3. http://www.ericsink.com/ - one of the best blogs about version
control
4. http://www.versioncontrolblog.com/ - another great blog about
version control
5. http://better-scm.berlios.de/comparison/comparison.html - VCS
comparison table
6. http://www.cmcrossroads.com/ - biggest resource about SCM
7. http://git-scm.org/course/svn.html - git for svn users
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