revision control with tortoisehg

Revision Control with TortoiseHg

(Team use)

Team version

Prepared by: Steve Teo (past tutor)Contributors: Tong Huu Khiem (current tutor)

CS2103 – Software Engineering

Before we begin…

These gray boxes have notes inside

Red box means instructions.Follow them.

Red, bold text are important things.

Notes clarify things and provides more in-depth knowledge

These instructions is tested with version 2.4.2 of TortoiseHg

Except the titles, of course

Moving on from individual use…• Version control is important for an individual developer.• Regular revision control helps a developer manage his/her code,

increasing productivity.• The Mercurial Revision Control System offers the advantage of

having a local repository With a local repository, commits and other repository operations can be

done offline at any time. Developers, especially those who have used RCSs such as Subversion

(which lacks the local repository feature), will find regular versioning with Mercurial a joy, not chore.

• However, you have yet to fully utilize the capabilities of a Revision Control System if you’re using it alone.

… to team use of a RCS• RCS is used to manage the codebase of software development

projects (which consists of teams of developers) in the industry, making it crucial to learn how to use it properly now.

• The Mercurial Revision Control System is fully capable of supporting team projects.

• Adopting a RCS for team use requires the establishment of a workflow and making sure team members follow it.

• In this first part, we shall learn a workflow to get a good grasp of it before proceeding with the practical itself.

Objectives• Learn the Central Repository Model

Role of the team’s centralized repository Basic team workflow

• Putting everything into practice Setup a Google Code Repository Checkout a remote repository Sync a local repository with a remote repo Configure username for identity purpose Push changesets Pull-Update changesets Merge changesets Resolve merge conflict

• Unleash Mercurial’s full power

Central Repository Model

The missing link• Every team member will have their own local repository.

However, there is no mechanism yet to share code changes with one another.

Team Leader

Team Leader’s

Local Repo

Member C

Member C’s Local Repo

Member A

Member A’s Local Repo

Member B

Member B’s Local Repo

• In the Central Repository Model, there is a central (remote) repository owned by the team

• Team members download (‘pull’) and upload (‘push’) changes between their own local repositories and the central repository.

• A team member’s local repository cannot share changes directly with other members’ local repositories.

• Developers can choose to push their changes to the central repository only when they are confident of their changes.

• Thus, it is not guaranteed that the central repository will always have the latest code.

• However, it is expected to contain the latest stable code.


Team’s Central Repo

Team Leader

Leader’s Local Repo

Member C Member C’s Local Repo

Member AMember A’s Local Repo

Member BMember B’s Local Repo


Basic team workflow

Push• Update your changes from the local repo to a remote repo



push changes

Revision/changeset• A revision is the set of changes whenever a push is

performed. Each revision is given a number. A revision is also known as a changeset. In this tutorial, we will use both terms interchangeably.

• A revision contains other important information such as the author of the changes and the summary of each change.

• Each successful commit will result in a new revision.• Each revision will definitely have one or more revision for

its parent except for the first revision, which will have zero.

Pull• Retrieve new changes from the remote repo to your local repo



pull changes

Update/Merge• Pulling changes only retrieves changes from the remote

repository into the local repository. However, the working copy is not updated in a Pull operation.

• You need to update the working copy to the latest version by using the Update command. If there are multiple heads (i.e. same file modified by multiple persons), you need to use the merge command instead.

updateMember A’s Local RepoMember A’s

Working Copy

• There are a few ways of doing a pull and update in one shot.• In Step 3 of “Putting everything into practice”, we will

show you how you can set up such behavior using TortoiseHg itself.

• For the command line gurus, you can use the hg fetch command to do pull and update in one shot (need to enable the fetch extension first).

15

Pull+update?

Pulling and pushing (Diagram)

16

Member B Member B’s Local Repo

Member A Member A’s Local Repo

2. push changes3. Te

lls h

im to

pul

l

1. makes some changes and commit

Team’s CentralRe

po

4. pull and merge

• In the above model, Member A commits some changes and pushes them to the Central Repository.

• Member A then informs the team to pull his changes off the Central Repository. Member B decides to do so and merges the changes from the Central Repository into his own repository.

• If any other member wishes to have the latest stable code, all they have to do is to pull off the Central Repository.

17

Pulling & pushing (explanation)

Putting everything to practice

Setup a Google Code RepositoryStep 1

Setup a Google Code Repository• In this guide, we shall use the excellent open source hosting site

Google Code as an example. However, note that your code will be available for checkout by anyone.

• There are other Mercurial repository-hosting sites such as BitBucket at https://bitbucket.org/, which offers free private repositories as long as access to the repository is kept to 5 users.

Note for CS2103/T students: Your project tutor will set up the Google Code account for you. Instructions under step 1 are for your information only. But you should follow from Step 2 onwards.

https://bitbucket.org/



Setup a Google Code RepositorySign up for a new project at http://code.google.com/hosting/

Choose Mercurial as your version control system

http://code.google.com/hosting/



Go to Source tab -> Checkout

Remember to note down the repository URL

Take note of your repository URL

Access your password

Setup a Google Code Repository

Remember of your googlecode.com password, too

You need this password to push changeset to Google Code

You can access all the project you have here

Setup a Google Code Repository

Browse the code in your repository by going to Source tab-> Browse

Setup a Google Code repository

Files will shows up as you commit code

View all the changes in your project by going to Source tab-> Browse

A commit graph will shows up as you commit code


Add your team members as Owners under the Administer tab -> Sharing

Emails of your team members go here


Remember to create a Google group for your team and add it to the activity notification under Administer tab-> Source

Add your team’s google group email here


Step 2Clone a repository

If you already have an existing repository of the project on Google Code (set up by one of your team members), you can clone it from the Google Code repository to your hard disk. Otherwise, skip to Step 3

Right-click on a new folder and select TortoiseHg - Clone

Clone a repository

Cloning allows you to duplicate the entire repository, copying all the existing contents to the destination as well as the whole revision history.

Paste the Google Code repo URL here. This slide explains where to find the Google code repo URL.

Clone a repository

Step 3Sync a local repositorywith a remote repo

If you have an existing local repository, you can also configure it to sync with the repo on Google Code

Click Synchronize

Sync a local repository with a remote repo

Choose https

Use the relative URL

Use “code.google.com”

Use “default” for alias

Add the Google Code repository URL as the default path


Save

You can also configure Post-Pull behavior for repositories

Select Post Pull

Update option will make TortoiseHg automatically update your repository whenever you pull some change


Step 4Configure username for accountability

In a team setting, you need to establish an identity so that you and your teammates know what you guys committed

Configure username for accountability

Select a repository and choose Repository Settings

Unser Commit group, enter the username & email that you want to associate your commits with

Use “name <email>” here


You can also set the username in the global settings. If there are no repository-specific settings specified, Mercurial will use the global settings.

This affects every repository on your computer


From now on, your name will show up in subsequent commitsThis commit username can be different from your Google Code username

Commits now have the author which you have just specified


Step 5Push changeset

After making some commits to our local repository, we are ready to push all of them into our Central Repository for the first time.

Right click on your local repo and choose Hg Workbench

Push changesets

In Hg Workbench, we will first preview the commits that are to be pushed.

Click Detect outgoing changes. This will compare the local and

remote repository, finding changes to be pushed

Push changesets

Click here to preview which changes will be going to the repo

These are the changes that is going to be pushed

Click Push to upload these to Google Code

TortoiseHg will find all the changes that need to be pushed

Push changesets

Then you will need to authenticate TortoiseHg to reach your Google code repository

Enter your Google code username

Push changesets

And your Google code password, as well. This is not your Google password. This slide explains where to get this password.

Push changesets

Enter your Google Code password

If the commits are pushed successfully, there will be no errors. You can look at the output log for more info in any case.

Push changesets

Success

You can also do a quick verification of the success of your commits by detecting changes for pushing again

Push changesets

Click here

This directly push changes, without checking. Not

recommended for now

Your commit was pushed

Push changesetsGo to your Google code repository, check the Source tab-> Changes

You should see that your commits were pushed successfully here

If you find it a chore to enter your login details every time you push changes or pull from a private repository which you have pull access from, you can store your login details using TortoiseHg.

Push changesets

Click “Synchronize” to open the sync panel at the bottom

Click on the lock to open the security panel

Key in your Google account details

Step 6Pull & Update changeset

Let’s say Greg have pushed his code. Now his friend, Holly decides to pull the changes into her currently empty local repository.

Pull & update changes

Again, open Hg Workbench

In Hg Workbench, you can check for new changes from repository


Check for changes from Google Code

When new changes are detected, you can accept and download them


Click to download changes below

The changes have been pulled into the local repository. However, we still need to update the working copy to the latest changes.


This means there are changes that is more up-to-date (2 and 3). You will need to update

You can update in Hg Workbench or right-click on the repository and use the popup menu


Click Update to open the update dialog

Use the default option to update to the latest changes


Once updated, everything is fine again. No more error message


• Finding it so troublesome to pull and then update? You can configure TortoiseHg to update for you by simply configuring the Post-Pull behavior as listed in Step 3: Sync a local repository with a remote repo

• Summary: Pulling only pulls the changesets into the local repository. You still need to update the working copy with the new changesets. Keep repeating this to yourself: Pull and Update

Pull & Update changes

Step 7Merge changesets

Merge changesets• You may encounter this common scenario

Greg pushed his code to the repository. Then Holly & Rowley pulled and updated Greg’s code. Rowley then made some changes, committed and pushed them. Meanwhile, Holly also made her own changes and was about to push the code.

• This can be summarized in the following timeline

Merge changeset

Greg

Holly

Rowley

Pushed

Pulled & Updated Commit new code

Pushed

Try to push

Commit new codePulled & Updated

time

Team Repository (Google Code)

In this situation, Rowley can’t push. He must merge his changes with Holly’sThis is how Google Code look like after Rowley has pushed his code

Merge changesets

Here, Holly check her code and detected one that need to be pushed

Merge changesets

When she push, however, there was an error. This is because she needs to pull Rowley’s code first

Merge changesets

Holly proceeds to pull Rowley’s code, seeing one changeset

Merge changesets

After Holly have pulled Rowley’s code, the repository look like thisNow, she need to merge her changes (4) with Rowley’s (5)

Merge changesets

The newly pulled changeset

Holly first select Rowley’s change and proceed with the merge

Merge changesets

Use Merge with local… to merge the new incoming changesets with yours

A summary of the upcoming merge is displayed on the 1st step of the merging process.

Merge changesets

Mercurial proceeds to merge and the merge results are shown on the 2nd step of the merging process.

Merge changesets

The process of Merging must be finalized with a commit to save the merge on the 3rd step of the merging process.

Merge changesets

The merge is done. Holly will now need to push the finalized merge commit back to the repository on Google Code

Merge changesets

The commit for the merge

The merge commit and Holly’s own commits earlier are marked for pushing

Merge changesets

And then they’re pushed to the remote repository

Merge changesets

• Has this whole section been mind-boggling? Remember, the goal of merging is to combine changes between changesets. Once the merge is complete, it has to be committed and then pushed back to the remote repository.

• Summary of merging steps : Pull the incoming changesets from the remote repository Merge the latest incoming changeset with the local working copy Commit the merge into the local repository Push the merge back to the remote repository

• Find out more about Mercurial’s merging: http://tortoisehg.bitbucket.org/hgbook/1.6/a-tour-of-mercurial-merging-work.html

Merge changesets

http://tortoisehg.bitbucket.org/hgbook/1.6/a-tour-of-mercurial-merging-work.html




Step 8Resolve merge conflict

• The merging scenario which was described in Step 7 is an example of a happy flow. There were no merge conflicts and this should be the case most of the time.

• In some cases, a merge conflict can result when two people were working on the same file and decided to commit their changes. When Mercurial merges both of their work, it realizes it cannot do so automatically on its own and thus requires intervention from the one who initiates the merge.

• Merge conflicts are settled by a user selecting which portion of the changed code should be in the finalized file.

• Merge conflicts can be avoided in Software Projects through proper software engineering and individual ownership of classes. However, should such a conflict occur, Mercurial is capable of handling it.

Resolve merge conflict

• Let’s look at a more specific example:Rowley and Holly both started with the same code. Rowley then edited one file, committed and pushed it. At the same time, Holly also edit that file, committed and was about to push it. This creates a situation where Holly need to merge her changeset and Rowley’s, as we have seen in the last section about merge

• Normally, if Holly and Rowley change different files, say file A for Rowley and file B for Holly, TortoiseHg will automatically merge, using the newer version of file A from Rowley and a newer version of file B from Holly

• However, since they both change one file, TortoiseHg can’t figure out whose version to use. This situation causes a merge conflict


Merge changeset

Rowley

Holly

Pulled & Updated Commit new code

Pushed

Try to push

Commit new codePulled & Updated

time

One file, project.txt for example

Create version A of project.txt

Create version B of project.txt

In this real example, Rowley and Holly started from Holly’s version of the code, where she add Stylizer.h and Stylizer.cpp


They both started from this revision

• Both Rowley and Holly decides to edit these files in their own way


Stylizer.hStylizer.cpp

Added a function called Stylize

[Stylizer.h], add:void Stylize(fstream one_file);

[Stylizer.cpp], add:void Stylizer::Stylize(fstream one_file){};

Added a function called Style_file

[Stylizer.h], add:void Style_file(fstream one_file);

[Stylizer.cpp], add:void Stylizer::Style_file (fstream one_file){};

Holly has edited the file and pushed her changeset to Google Code


Holly’s new changeset

While pushing his commit, Rowley got an errorThen he proceeds to do a pull


After Rowley pulled, he saw that Holly have one changeset that he doesn’tNow he need to merge his change with Holly’s


The changeset Rowley pulled

Again, this is done using the Merge with local option


Use Merge with local… to merge the new incoming changesets with yours

A dialog box shows up, summarizing the upcoming merge


However, a conflict showed up while mergingRowley now need to resolve this before continuing


Click here to resolve the merge conflict

The Resolve conflicts dialog shows up


Actions:Mercurial Resolve – Let Mercurial resolve it automatically (trivial)Tool Resolve – Let the default merge tool resolve itTake Local – Takes the version of the file in local working copy.Take Other – Take the other version of the file which is not the local working copy.Mark as Resolved – Marks the file as resolved

For example, if you use Tool Resolve, TortoiseHg will launch kidff3 and you can resolve the conflict there


After all conflicts are resolved, close the dialog box and commit the merge, similar to Step 7: Merge changeset


And this is how it is in Google code repository


The conflicted merge

• The example above was the resolution of a simple merge conflict.

• Even though Jane and Steve edited the same file, their changes were on different lines. Mercurial or the default Diff program was smart enough to resolve it automatically on its own. Therefore, Steve did not need to choose which changes he wanted.

• In other complex cases, you and your team mates could have edited the same section of code. In those cases, you have to use the Diff program to select which sections of code you want in the final merged code.

• As mentioned in the beginning of this step, you can avoid most of those cases by maintaining individual ownership of files and proper software engineering.


Unleash Mercurial’s full power

• So far, you were introduced to the Central Repository Model.• The Central Repository Model is an adaptation of the Centralized

model supported by a group of RCS called Centralized Revision Control Systems (CRCS for short), of which the most notable is Subversion (SVN for short).

• In CRCS, there is a central repository hosted on a remote server but no local repositories. Developers synchronize changes directly to the central repository and a network connection is required for most repository operations.

Centralized Revision Control System

• Compare this with the Central Repository Model on Slide 9


Team Leader

Member C

Member A

Member B

Centralized Model

• Mercurial belongs to a group of RCS known as Decentralized Revision Control Systems (DRCS), which includes Git.

• DRCS uses the Decentralized Model: repositories are decentralized and repository configuration is flexible.Hence the workflow can vary differently from team to team.

• In the general model, every team member has his/her own remote repository in addition to their own local repository. There is no such thing as the central repository.

Distributed Revision Control System

Pulling & Pushing in Decentralized Model

Member B

Member B’s Local

Repo

Member A

Member A’s Local

Repo

Member A’s

Hosted Repo

1. pull and merge

3. push changes

4. se

nds p

ull r

eque

st

2. makes some changes and commit

Member B’s

Hosted Repo

5. pull and merge

6. push changes

Pulling & Pushing in Decentralized Model• You can see that Member A pulls the latest changes off Member B’s

hosted repository and merges the changes with his local repository. Now that his local repository is updated, he then commits his own changes and pushes them to his hosted repository.

• Member A then informs the team to pull his changes off his hosted repository. Member B decides to do so and merges the changes from Member A’s hosted repository into his own local repository.

• Each of the members does not pull off from one another’s local repository. Instead, they pull off changes from one another’s hosted repository.

Advantages of DRCS in brief• Presence of the local repository allows you to commit code and

push the changes only when you are ready• No need for an Internet connection to commit changes or access

your local repository, which means full benefits of version control anytime anywhere.

• Flexible organization of repositories as workflow does not always have to be centralized

• You can choose whether or not to pull from repositories and condemn your friend’s buggy code until it is fixed.

• And many many more…

revision control with tortoisehg

Documents

local repository feature

team members local repository

central remote repository

local repositorywith

central repository modelrole

repository operations

members local repositories

team use