Copy (2) of 3_version_control

8/2/2019 Copy (2) of 3_version_control

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Outline

1 Introduction

2 Let there be a Repo!

3 But Why commit ?

4 Collaborating with Mercurial

5 Conclusion

FOSSEE (IIT Bombay) Mercurial 2 / 42
http://find/http://goback/


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Objectives

At the end of this session, you will be able to:

Understand what is Version Control and the need

for it

Create and use repository on a daily basis

Clone existing repositories, from the web

View the history of a repository

Make changes to a repository and commit themWork collaboratively with a team

http://find/


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Introduction

Outline

1 Introduction


3 But Why commit ?


5 Conclusion

http://find/


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Introduction

What is Version Control?

A way to track changes made to files over time, bykeeping copies of files as we change them.


I d i
http://find/


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Introduction

Home-brewed

An example of a home-brew Version Control system

$ ls

a.out id1.txt id2.txt identifier.cpp

id.txt lex pda1.cpp pda2.cpp pda.cppFOSSEE (IIT Bombay) Mercurial 6 / 42

I t d ti
http://find/


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Introduction

Problems

Name and changes made are not related or linked.

Cant track sequence of changes made to a file.

Does not scale.


Introduction


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Introduction

The need for Version Control

To err is Human . . .

Tracking the history and evolution of a projectTo collaborate effectively on a project

To efficiently track down bugs and pin-point the

changes that caused it


Introduction


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Introduction

How does it work? Analogy

It is, in some ways, similar to playing an Video game.

We play games in stages

Once we finish a stage or a task we SAVEWe continue playing

But, if necessary, we could choose from one of the

saved states and start from there

We could alter the course of the game

http://find/


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Introduction


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Introduction

Installation

sudo apt-get install mercurial

TortoiseHg$ hg

$ hg version


Let there be a Repo!


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p

Outline

1 Introduction


3 But Why commit ?


5 Conclusion




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p

We need a repo!

A Repository (repo) is where all the action is!

Project files along with a special directory thatstores all the changes

We take snapshots of the whole repository; not

individual files.




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Initializing a repo

$ hg init

Creates a fresh repositoryAdds a .hg directory to our working directory

.hg directory keeps log of changes made henceforth


http://find/


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Status report

hg status gives the status of our repo

Use it often; at least as a beginnerhg help command gives us help about

command




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Status codes

M = modified

A = added

R = removedC = clean

! = missing

? = not tracked

I = ignored




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Adding files

From hg status we know, none of the files are

being tracked, yet.

hg add asking hg to track these filesAs expected hg status prepends an A to the file

names.

? - - > A

! - - > R (hg remove)




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Taking Snapshots

hg commit

Asking Mercurial to take a snapshot; remember

the changes made to the repository.

-u FirstName LastName

-m Commit message a description of

changes committed.




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Thumbnail views

hg log gives the log of the changes made

A changeset is an atomic collection of changes

to the files (between successive commits)

Log information

changeset: Identifier for the changeset

user: Details of user who created the changeset

date: Date and time of creation

summary: One line description




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User information

User information is set in the hgrc file

It can be set globally or local to the projectGlobal hgrc

$HOME/.hgrc Unix like systems

%HOME%\.hgrc Windows



Ad i


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Advice: commits, messages

Atomic changes; one change with one commit

Single line summary 60 to 65 characters long

Followed by paragraphs of detailed descriptionWhy the change?

What does it effect?

Known bugs/issues?

etc.


But Why commit ?

O tli
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Outline

1 Introduction


3 But Why commit ?


5 Conclusion


But Why commit ?

O ti l h d?
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Operational overhead?

But why do we commit?

Isnt all this just adding to operational costs?

Isnt all this a waste of time?

No! You shall see the benefits, soon!

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But Why commit ?

Vi i Ch


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Viewing Changes

hg diff all changes since last commit

- this line was deleted

+ this line was added


But Why commit ?

Re ision n mbering


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Revision numbering

changeset: n:cbf6e2a375b4

n is the revision numberThe revision number is local to a repository

cbf6e2a375b4 is the unique identifier

http://find/


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Collaborating with Mercurial

Outline


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Outline

1 Introduction


3 But Why commit ?


5 Conclusion



Cloning Repositories
http://find/


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Cloning Repositories

hg clone SOURCE [DEST]All hg repositories are self-contained



Sharing Repositories


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Sharing Repositories

hg serveCan be cloned with

hg clone http://my-ip-address:8000

We share a central repository; work on our localcopies.

Set write permissions in .hg/hgrc

[web]push_ssl=False

allow_push=*



Sharing Changes
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Sharing Changes

Use hg push to push your commits(changesets) to the central repository



Pulling Changes
http://find/


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Pulling Changes

hg incoming shows new changesets in the

server

To get these changesets, we use hg pullThese changes do not affect our working directory

hg parent shows the parents of the working

directory



Pulling Changes
http://find/


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Pulling Changes . . .

hg update will update the working directoryUpdates to the tip if no revision is specified

tip is the most recently added changesetCan specify revision number to update to

hg tip shows the tip of the repository



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Merging


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Merging

Pull and merge, when

abort: push creates new remote heads!hg merge will merge the two diverged heads

commit after you have merged!



Simultaneous Changes


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Simultaneous Changes . . .

outgoing shows the changesets that will be

pushedhg push works!

Look at the Change graph!



Simultaneous Conflicting Changes


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Simultaneous Conflicting Changes

What if the changes conflict? overlapping edits

hg push fails; hg pull; hg merge

You now get a diff view with 3 panes

First current fileSecond changesets that you pulled

Third file before you made your changes

Resolve conflict and save

hg commit; hg pushLook at the Change graph!



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Conclusion

Summary I


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Summary I

In this session, we have learnt to:

initialize new repositories, using hg init

check the status using hg status

get help for any command using hg help

commit changes or take snapshots using

hg commit

view the history of a repository using hg log

set the user info in the global hgrc fileundo changes using hg revert

view changes using hg diff


Conclusion

Summary II


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Summary II

use revision numbers as arguments to various

commands

clone repositories using hg clone

server repositories using hg serve

push changes using hg pushpull changes using hg pull

update working directory to latest revision using

hg updatemerge two heads using hg merge

resolve merge conflicts using hg resolve


Conclusion

References


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A Visual Guide to Version Control

Version Control for the Masses

(Illustrated) Intro to Distributed Version Control

Understanding Mercurial

A Tutorial on Using Mercurial

Hg Init: a Mercurial tutorial

Beginners GuidesSoftware Carpentry

http://betterexplained.com/articles/a-visual-guide-to-version-control/http://karlagius.com/2009/01/09/version-control-for-the-masses/http://betterexplained.com/articles/intro-to-distributed-version-control-illustrated/http://mercurial.selenic.com/wiki/UnderstandingMercurialhttp://mercurial.selenic.com/wiki/Tutorialhttp://hginit.com/http://mercurial.selenic.com/wiki/BeginnersGuideshttp://software-carpentry.org/4_0/vc/http://software-carpentry.org/4_0/vc/http://mercurial.selenic.com/wiki/BeginnersGuideshttp://hginit.com/http://mercurial.selenic.com/wiki/Tutorialhttp://mercurial.selenic.com/wiki/UnderstandingMercurialhttp://betterexplained.com/articles/intro-to-distributed-version-control-illustrated/http://karlagius.com/2009/01/09/version-control-for-the-masses/http://betterexplained.com/articles/a-visual-guide-to-version-control/http://find/http://goback/

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Copy (2) of 3_version_control