05 - Merge Management

MERGE MANAGEMENT

TRAINING GOALS

Describe problems and risks emerging during merge operations in

Show how to mitigate those risks and avoid problems related to

merging

TRAINING PLAN

1. What is merging?2. Why do we need to manage merging?3. Merging machinery4. Branch types5. Merging operation – maturity testing6. Merging in action7. Advanced merge management8. Criteria of successful merge

INTRODUCTION TO MERGE MANAGEMENT Basic ideas and principles

WHAT IS MERGING?

• In general sense:combination of two (or more) different objects into the whole in the form of new object with unified properties

• Applicably to Version Control Systems:fundamental operation that reconciles multiple changes made to a revision-controlled collection of files

WHY DO WE NEED TO MANAGE MERGING?

1. Result of merging often might be unpredictable

2. Nobody can guarantee that result of merging is the one you really wanted to achieve

3. Few people know the machinery of merging process

4. If something unpredictable happened during merging, almost nobody can explain why.

5. This is all because merging is the one of the most non-trivial operations of version control systems

LET’S DIVE INTO THE MERGING MACHINERY

COMMON BUZZWORDS OF MERGING MACHINERY

diff patch

branch merge

conflict cherrypicking

diff patch

branch merge

There are two diffs:diff and diff3

DIFF (TWO-WAY MERGE)

Based on the longest common subsequence (LCS) algorithm

Not to confuse with longest common substring algorithm

Complexity of LCS algorithm is O(mn); m, n – lengths of the strings

Therefore, diff works using line by line comparison

Uses four formats: normal, context, unified, ed Can compare directories and their content

recursively But does not track directories move/rename

DIFF (TWO-WAY MERGE)

DIFF3 (THREE-WAY MERGE)

Manual comparison of three files

Automatic merging

Generation of conflict situations

Textual representation of the conflicts

Diff3 utility is the basis for:

… as merging into mine the changes that would turn older into theirs

You can think of diff3 as subtracting older from theirs and adding the result to mine …

diff patch

branch merge

patch is often complementary to

the diff

Useful utility for applying specific source code change set to the working copy

Reversed diff Imitation of distributed version control in

centralized VCSs

You can think about patch – as a:

Merging functionality in DVCSs is implemented via series of subsequent patches applied.

There is no patch format extension for directories structure modification. Beware about move, rename and delete operations

svn merge command is like patch, but with additional special abilities such as: tree structure changes tracking and mergeinfo tracking

Result of svn diff command is the fully functioning patch file, but with little bit more limited representation abilities (subset of patch format)

Patch is also often called changeset

Interesting facts about patch:

WC (working copy)

create patch

apply patch

svn diff > patchfile.patch

patch -p0 < patchfile.patch

diff patch

branch merge

merge has no sense without branches

BRANCH

No merge without branch

No branch without merge

BRANCH

Separate isolated parallel development line (codebase)

Operation of separate development line creation (branching)

Set of files having common ancestor with another set of files

Another folder in repository (usually in /branches parent directory) of centralized VCS

Dedicated private place in distributed VCS

You can think about branch as:

BRANCH TYPES

svn merge sourceURL1[@N] sourceURL2[@M] [WCPATH]svn merge -r N:M SOURCE [PATH]

Purpose of the branches, their contents and types directly affect the merging operation workflow and its

results

Merging operation is highly dependent on source and target branches

BRANCH TYPES

Purpose

Maturity

Codebase disparity

Independence

Duration Branch types

features

BRANCH TYPES

Branch types

Experimental

SupportRelease

diff patch

branch merge

merge is the most advanced operation

VCSs have

Reconciliation of multiple changes made to a revision-controlled collection of files

Application of the differences between two sources to a working copy path (svn merge, svn update)

Operation of joining two or more development histories together (git merge)

Reintegration of the whole branch (or its part) into another branch

Process of two or three files comparison: 2-way merge and 3-way merge

Automatically generated result of 3-way merge: automerge

You can think about merge as:

MERGE. USE CASE

diff patch

branch merge

conflicts happen when there are difficulties with

merging

CONFLICT

It is difficult to avoid conflict situation during team work

CONFLICT

Conflict – is a state of one or more working copy artifacts assuming that: The same source code lines have been modified by

different users Artifact properties have been modified by different

users VCS cannot resolve modifications of directory

structure have been made by different users

Conflict situations are potentially produced by: svn update svn merge

GENERAL CONFLICT RESOLUTION WORKFLOW

Update working

copy with conflicting changes

Use one of the conflict resolution

options suggested

by VCS (svn

resolve)

Or edit files manually

saving final version and running svn resolved command

Commit resolved changes

CONFLICT RESOLUTION OPTIONS

• postponep• diff-fulldf• edite• resolvedr• mine-conflictmc• theirs-conflicttc• show all optionss

diff patch

branch merge

cherrypicking means replication of single

change

MERGING IN ACTIONPractical example of merging

REVISIONS HISTORY>: svn log

svn://localhost/ParseCmdLine/branches/experimental/experimentalOptions --stop-on-copy

>: svn log svn://localhost/ParseCmdLine/trunk

------------------------------------------------------------------------r42 | svn | 2011-02-26 20:29:59 +0200 (Sat, 26 Feb 2011)------------------------------------------------------------------------r41 | svn | 2011-02-25 20:49:10 +0200 (Fri, 25 Feb 2011)------------------------------------------------------------------------r40 | svn | 2011-02-25 20:44:40 +0200 (Fri, 25 Feb 2011)------------------------------------------------------------------------r38 | svn | 2011-02-25 00:39:06 +0200 (Fri, 25 Feb 2011)------------------------------------------------------------------------r37 | svn | 2011-02-25 00:24:47 +0200 (Fri, 25 Feb 2011)------------------------------------------------------------------------r36 | svn | 2011-02-25 00:20:28 +0200 (Fri, 25 Feb 2011)------------------------------------------------------------------------

r43 | svn | 2011-02-28 16:26:44 +0200 (Mon, 28 Feb 2011)------------------------------------------------------------------------r39 | svn | 2011-02-25 20:41:01 +0200 (Fri, 25 Feb 2011)------------------------------------------------------------------------r33 | svn | 2011-02-24 13:24:31 +0200 (Thu, 24 Feb 2011)------------------------------------------------------------------------r32 | svn | 2011-02-24 13:21:44 +0200 (Thu, 24 Feb 2011)------------------------------------------------------------------------r31 | svn | 2011-02-24 13:16:34 +0200 (Thu, 24 Feb 2011)------------------------------------------------------------------------r30 | svn | 2011-02-24 12:25:47 +0200 (Thu, 24 Feb 2011)------------------------------------------------------------------------r28 | svn | 2011-02-24 12:14:14 +0200 (Thu, 24 Feb 2011)

REVISIONS HISTORY>: svn log

svn://localhost/ParseCmdLine/branches/experimental/experimentalOptions --stop-on-copy

>: svn log svn://localhost/ParseCmdLine/trunk

MERGING RANGE OF REVISIONS

>: svn merge svn://localhost/ParseCmdLine/trunk svn://localhost/ParseCmdLine/branches/experimental/experimentalOptions –r 39:43

REINTEGRATING A BRANCH

>: svn merge svn://localhost/ParseCmdLine/branches/experimental/experimentalOptions svn://localhost/ParseCmdLine/trunk --reintegrate

MERGING TWO TREES

>: svn merge svn://localhost/ParseCmdLine/branches/experimental/experimentalOptions svn://localhost/ParseCmdLine/trunk --ignore-ancestry

DIFF3 VS MERGE

diff3 always ignores ancestry merge takes into account ancestry by default Therefore, repository should store information

about: Branching (svn copy operations) Merging (svn merge operations, revisions, baselines,

etc) Tree modifications (files copying, deletion, movement,

etc) Operations sequence

Before the release of Subversion 1.5 this functionality was implemented in svnmerge.py

In Subversion 1.5 it is called merge tracking

MERGE TRACKING

Reduces the bookkeeping overhead for branch maintenance

Allows to avoid common cases of the "repeated merge" problem

Allows cherry-picking of changes

Allows outputting list of revisions available for merging

Support of bidirectional merges

Support of blocking changes

Support of merge rollbacks

svn merge -c REV SOURCE WC svn merge svn://localhost/ParseCmdLine/trunk svn://localhost/ParseCmdLine/branches/experimental/experimentalOptions –c 43

CHERRYPICKING

/experimental

22 23 24 25 … 39 40 41 42 43

/trunk

Revision number

END OF SECTION

MERGE. MATURITY TESTINGProving that nothing is so simple as someone says

MERGE. MATURITY TESTING

There are several cases proving that…you cannot fully trust automerge

Standard conflict handling

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

Merging operation maturity test cases:

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

Making sure same source code lines have been

modified by different users

Diff3 Subversion Git

Works as expected

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

Works as expected

Sometimes problems emerge at the beginning

and ending of the file

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

Fails Works as expected

Works as expected

handling identical files from

different working copies

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

Merging operation maturity test cases:Diff3 Subversion Git

handling identical files from different working copies, but with minor adjacent

changes

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

Merging operation maturity test cases:Diff3 Subversion Git

Works as expected

adjacent changes from different working copies

BOF/EOF Stingers

Identical Twins

X-Tuplets

Hungry Blobs

Unique anchors

using additional heuristics during diff for covering

special cases of merging

Fails Fails Fails

One more example of faulty automerging:

ADVANCED MERGE MANAGEMENTMore complex issues related to merging

BRANCHES INHERITANCE

RELATIONBRANCH TYPE trunk support release experimental

trunksupportrelease

experimental

parent

There are certain branch creation and inheritance restrictions which will be described

by filling in table shown below

trunksupportrelease

experimental

parent

Trunk cannot be the child of any other branch

trunk +support -release -

experimental -

parent

Support branch can be inherited only from trunk

trunk + +support - +release - -

experimental - -

parent

Release branches can be inherited both from trunk and support branches

trunk + + +support - + +release - - -

experimental - - +

parent

Experimental branches can be inherited from any type of branch except release branch

SUPPORT AND RELEASE BRANCHES

/trunk

/1.0.x

/1.1.x

/1.x.x

/2.0.x

/1.2.x

support branch

release branch

EXPERIMENTAL BRANCHES

/trunk

experimental branch

/db_refactoring

/UI_integration

/UI_lazy_loading

/Layout_rework

/3-column

/1.x.x

/l18n_embedding

support branch

TO MERGE OR NOT TO MERGE?

DESTINATIONBRANCH TYPE trunk

RELATION parent parent child parent child parent childtrunk parent

parent

support release experimental

support

release

experimental

There are certain merging restrictions which will be described by filling in table shown

We will fill in it step by step in order to understand all aspects of the advanced merge

management.

RELATION parent parent child parent child parent childtrunk parent - - +

parent - +child - - -

parent

child + + - -parent +

child + + - - + +

support

release

experimental

Final result will look as follows

Logically excluded cases of merging Cases excluded by branch inheritance and creation rules Allowed case of merging Disallowed case of merging operation

parent

support

release

experimental

Trunk can be only parent branch

experimental - - +

parent

support

release

experimental

Merging from parent to parent of the same branch seems to be merged into itself. It

makes sense only as a conflict which is not the case of merge we're considering

parent

support

release

experimental

Branch cannot be parent to itself

RELATION parent parent child parent child parent child

trunk parent

parent -child - -

parent +child + +

support

release

experimental

There are cases automatically excluded by branch creation and inheritance rules

experimental - - +

parent

child - -parent - -

child -parent - -

child -

support

release

experimental

There are cases automatically excluded by branch creation and inheritance rules

experimental - - +

parent

support

release

experimental

This is the result of exclusion merging cases by logic and branches creation and

inheritance rules.

We will be filling in empty cells

RELATION parent parent child parent child parent childtrunk parent -

parent

child -parent

parent

support

release

experimental

Support branches are fully independent, they are not assumed to be merged with trunk or

other support branches

/trunk

/1.x.x

RELATION parent parent child parent child parent childtrunk parent - -

parent -child -

parent

child + +parent

support

release

experimental

Purpose of release branch is maturing the release

It is expected that only bugfixes will be merged to parent branch and no changes will be merged from parent branch

parent -child -

parent

child + +parent

support

release

experimental

Purpose of release branch is maturing the release

/trunk

/0.2.x

/1.x.x

/1.0.x

parent -child - -

parent

child + + -parent

support

release

experimental

Child to child relation represents sibling branchesNo merge between sibling release and support branches is allowed

parent -child - -

parent

child + + -parent

support

release

experimental

Child to child relation represents sibling branches

/trunk

/1.x.x

/1.0.x

parent - +child - -

parent

child + + -parent +

child + + +

support

release

experimental

It is allowed to merge experimental branches with any type of parent branch

/trunk

/UI_integration

/Layout_rework

/3-column

parent

child + + - - + +

support

release

experimental

No merge allowed between sibling experimental and any type of other branch (except experimental)

/trunk

/UI_integration

/1.x.x/1.0.x

/UI_integration

/Layout_rework

/3-column

parent

child + + - - + +

support

release

experimental

Final picture

Total number of cells Number of cells with logically excluded cases Number of cells with cases excluded logically and using

branch inheritance rules Allowed case of merging Disallowed cases introduced by merging rules

SUPPORT AND RELEASE BRANCHES

/trunk

/1.0.x

/1.1.x

/1.x.x

/2.0.x

/1.2.x

support branch

release branch

disallowed merge operation

allowed merge operation

EXPERIMENTAL BRANCHES

/trunk

/db_refactoring

/UI_integration

/UI_lazy_loading

/Layout_rework

/3-column

/1.x.x

/l18n_embedding

experimental branch

support branch

disallowed merge

allowed merge

CONCLUSION

HOW WOULD YOU KNOW THE MERGE IS APPROPRIATE?

Make sure source and target branches are compatible for merging

HOW WOULD YOU KNOW THE MERGE IS SUCCESSFUL?

Don’t leave merges unfinished

Run unit-tests and inspections afterwards

Formal criteria: There are no conflicts Code compiles Unit-tests run successfully

Conceptual criteria: Implemented features do not have logical and

architectural contradictions Whole codebase correspond to the introduced

concepts In case of intersection between merged features

functionality it should lead to additional development

AFTERWORD

05 - Merge Management

Technology

Transcript of 05 - Merge Management

Duplicate Record Merge: Patient Merge Technical ManualApril 1998 Duplicate Record Merge: Patient Merge Technical Manual iii Revised November 2009 Version 7.3 Patch XT*7.3*113 Preface

Merge and Quick Sort - Islamic University of Gazasite.iugaza.edu.ps/.../Merge-and-Quick-Sort.pdf · Merge and Quick Sort Lawrence M. Brown Merge Sort Tree • Visualize a merge sort

Letter Automation Letter Management Organize Contacts Template Management Simplified Mail merge & email merge Double Productivity with.

Mail Merge Concepts - Fairfield UniversityMail Merge - Outlook • Finalizing the merge. – You will have to return the merge to step 1 to choose the type of merge you want to perform.

Mail Merge - Create Welcome Letter - Property Management

EHR & MU for HIM Professionals Patient Merge Resource Patient Management System.

TRAFFIC MANAGEMENT STRATEGIES FOR … management Strategies for Merge Areas in Rural Interstate Work Zones 1 TRAFFIC MANAGEMENT STRATEGIES FOR MERGE AREAS IN RURAL INTERSTATE WORK

FP6 – Priority 2.3.2.9 Improving Risk Management ......Doc b - EMW comments included Draft 2.8 04/02/05 Merge of NSW & EMW comments 3.0 02/03/05 Second official version to be released

Faster Sorting Methods Chapter 12. 2 Chapter Contents Merge Sort Merging Arrays Recursive Merge Sort The Efficiency of Merge Sort Iterative Merge Sort.

Export Client Details with Mail Merge - Reckon · 2020. 4. 28. · 2. Create the Mail Merge template. First, you will need to create a mail merge document for Practice Management

On the Nature of Merge: External Merge, Internal …home.uni-leipzig.de/muellerg/citko05.pdfOn the Nature of Merge: External Merge, Internal Merge, and Parallel Merge Barbara Citko

RHO 10 Website CHT INFORMATION SYSTEM FILE MANAGEMENT MAIL MERGE RHO 10 Website CHT INFORMATION SYSTEM FILE MANAGEMENT MAIL MERGE Louie T. Binondo IT Programmer.

White Paper: Branch Management and Atomic Merge in a Continuous Integration Environment

Algorithms: Sorting. Rand Sort. Compare-and-exchange. Merge Sort. Quick Sort. Odd-even merge sort. Bitonic merge sort.

Lesson 7: Mail Merge and Related Operations 7 MAIL MERGE ...

COMP1405 Ch6 Sorting - Carleton Universitypeople.scs.carleton.ca/.../ProcessingNotes/COMP1405_Ch6_Sorting.pdf · Merge Sorts Merge Sort, Polyphase Merge Sort, Strand Sort Non-Compairon

Data Management Seminar, 8-11th July 2008, Hamburg WinDEM - Merge Files.

Document Management and Merge Marilyn Edmond Technical Consultant Carl Hoffman Technical Consultant.

SORT/MERGE Utilities User's Guide - Atossupport.bull.com/ols/product/system/gcos7/gcos7... · DPS7000/XTA NOVASCALE 7000 SORT/MERGE Utilities User's Guide File and Volume Management

Mail Merge Magic! Using Mail Merge for Student Certificates

Duplicate Record Merge: Patient Merge Technical ManualApril 1998 Duplicate Record Merge: Patient Merge Technical Manual iii Revised November 2009 Version 7.3 Patch XT7.3113 Preface