Essentials Of Rational Clearcase Module 7: Integrating Parallel Development

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IBM Software Group

Essentials of Rational ClearCase Module 7: Integrating Parallel Development

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Objectives Upon completing this module, you should be able to: 

Discuss when it is advantageous to branch

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List common branch types and explain when you might use them

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Perform advanced merges

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Merge and compare non-ClearCase files

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Topics  Branching  Branching — review  Why branch?  Types of branches  Instantiating branch types  Merging  Performing special types of merges • Unreserved checkout • Selective merge • Subtractive merge  Merging and comparing non-ClearCase files 3

Branching: Review  Branching is a technique to isolate change and enable parallel development  Branching controls the public and private nature of work  Branch only when you want to make changes  Typically, parallel branches are eventually merged into a resulting product  Configuration managers, ClearCase administrators, or project leads typically define the organization branching and merging policies 4

Why Branch?  When you need project level parallel development of a common base (ports, spin-offs)  When you want to isolate aspects of the product’s evolution (release area, patch area, development area)  When you work on a long-range task and want to save and baseline your own work (private branches)  When you are working on a new feature and don’t want to have an impact on other developers  When you need to organize your work by location for use with ClearCase MultiSite 5

Types of Branches: Integration Branches  Branches designated for integrating development work  Allows you to work on multiple development threads concurrently  Examples include  /main  Project branches  Release branches  Feature branches

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Integration Branch Example: Project Branch  Branch used for each separate releasable product  All development for a particular project occurs only on the project branch  Can be just /main in simple environments

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Integration Branch Example: Release Branch  Branch designated for holding official releases of a product  Facilitates tracking changes among releases  Keeps version trees compact

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Integration Branch Example: Feature Branch  Branch designated for work on a specific feature  Facilitates tracking the development of individual modules and integration of the modules into project development branches

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Types of Branches: Maintenance Branches  Branch to track bug fixes and integrate them into project or release branches  Can generate patch versions  Several maintenance efforts in parallel may require a maintenance Integration

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Types of Branches: Developer Branches  Branch designated for long-range or high-risk individual development  Facilitates tracking the development of individual modules and integration of the modules into project and release branches

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MultiSite Branches  ClearCase MultiSite replicates and synchronizes VOBs across distant sites  Branches support parallel development across sites  Branches are ‘mastered’ by individual sites  Some integration may occur at replicated sites  One site is usually responsible for ‘release’ branch

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Viewing Branch Types

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Creating Branch Instances Using the Config Spec  Once a branch type exists, you can create instances of that branch type  Preferred method of instantiating branch types is using the –mkbranch clause in the config spec  The -mkbranch clause can be used to implement complex branching policies and to ensure consistent branching of elements

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Multiple-Level Auto-Branching  A config spec can include a “cascade” of -mkbranch rules: element * CHECKEDOUT element * /main/r2_int/pat_r2/LATEST element * /main/r2_int/LATEST -mkbranch pat_r2 element * R1 -mkbranch r2_int

 Check out continues to create branches until version zero on the new pat_r2 branch is created 15

Multiple-Level Auto-Branching (cont.) Rule 1: Rule 2: Rule 3: Rule 4:

element element element element

* * * *

CHECKEDOUT /main/r2_int/pat_r2/LATEST /main/r2_int/LATEST -mkbranch pat_r2 R1 -mkbranch r2_int

util.c after check out with the above config spec util.c before check out

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Multi-Level Auto-Branching: Write Config Specs 1.

2.

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Topics  Branching    

Branching — review Why branch? Types of branches Instantiating branch types

 Merging  Performing special types of merges • Unreserved checkout • Selective merge • Subtractive merge

 Merging/comparing non-ClearCase files 18

Merging an Unreserved Checkout  You cannot check in an unreserved checkout if there are successor versions  The unreserved checkout must be merged with LATEST before you can check in

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Merging an Unreserved Checkout (cont.) There are two checkouts: one reserved and one unreserved

After Alex checks in his reserved checkout

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After Pat merges Alex’s changes into her version and checks in

Selective Merge  Selects changes from specific versions from a branch to merge  Use the –insert option with merge command  No merge arrow in Version Tree Browser

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Selective Merge: Example Scenario: Integrate bug fix changes of /r1_bugfix/3 into /r2 branch

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Subtractive Merge  Removes changes made in one or more of its predecessors from a checked-out version  The –delete option indicates the version or range of versions to subtract  No merge arrow in Version Tree Browser

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Subtractive Merge: Example Scenario: The multi-thread algorithm implemented in element versions 2 and 3 contains a fatal flaw. How do you back out those changes, but retain subsequent good changes?

Back out only these changes

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Merging Non-ClearCase Files  Use the ClearCase Diff Merge tool to merge files not under ClearCase control Example: cleartool merge –out newfile.txt c:\file1.txt c:\file2.txt  Use the Diff Merge tool to merge non-ClearCase files with ClearCase elements Example: X:\Hardware\src>cleartool merge -g -to util.c c:\file1.txt 25

Comparing Non-ClearCase Files  Use the ClearCase Diff Merge tool to compare files not under ClearCase control Example: cleartool diff -g c:\file1.txt c:\file2.txt

 Use the Diff Merge tool to compare non-ClearCase files with ClearCase elements Example: X:\Hardware\src>cleartool diff -g util.c c:\file1.txt

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Module Review  Why might you want to create a branch?  How do you know what branch types are available?  What is the recommended way to create branch instances?  What do you do if you want to check in an unreserved checkout, but there are successor versions?  What is a selective merge? Why would you perform one?  What is a subtractive merge? Why would you perform one? 27

Module Lab  In this lab, you perform the following tasks:  Use the ClearCase GUI to view branch types  Perform a selective merge  Use the command line interface to • Compare and merge non-ClearCase files • Perform a subtractive merge

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