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Practical Git

Practical Git

This is a discussion on Git, the version control system. It is intended for folks with:

  1. Limited or no knowledge of any version control system
  2. Experience with Centralized Version Control Systems
  3. Experience with DVCS, but specifically git.

It covers the basics of version control, DVCS, and then goes on to describe Git in a practical way, with exercise to get the team quickly started on using Git.

It also talks a bit about how Git works internally, giving insights into the .git directory in each repository in order to demystify the commands.

It then moves on to Git workflows usable for various teams and also covers a one-line glossary of terms a person is most likely to encounter when using Git via CLI or through any UI tool.

Text Transcript

Slide 1:   Practical Git
Introduction (And Beyond)
                          @nikhilwanpal | NikhilWanpal


Slide 2: Version Control
 (The non-developer way)
                         @nikhilwanpal | NikhilWanpal


Slide 3:                       “With review comments from Guide”
                      “Modifications based on new
                      comments”
                      “Changes for team presentation”
                      “Changes for presentation at
                      conference, for novice audience”
                      “Merged changes: team and
                      conference”
                      “Cosmetic changes”
Version Control
  (The developer way)
                                       @nikhilwanpal | NikhilWanpal


Slide 4: Version Control Systems
Types:
1.  Local
2.  Centralized (CVCS): svn, cvs
3.  Distributed (DVCS): git, mercurial
                                       @nikhilwanpal | NikhilWanpal


Slide 5: Once upon a time..
● There was a Linus
● Then came Linux
● Then came the interest of the community and contributor boom
● Contributors distributed through time and space.
● The central person would become overworked, loaded.
● Need for distributed management.
● (skipping some events..) Birth of Git: To handle far complex, large and distributed
  teams. (than us)
● ..and then, came the interest of the community and contributor boom… (git
  uses git to version control git!)
                                                                     @nikhilwanpal | NikhilWanpal


Slide 6:                 CVCS                         Vs                   DVCS
1. Central Server, that manages the truth.      1. Distributed, no single location of truth.
2. Clients do checkout snapshots.               2. All clients are mirrors; servers; truth.
3. Weak clients                                 3. Fully functional clients
4. Server needs tending to: backups,            4. Self maintaining, recoverable from mirrors;
   maintenance etc.                                (of course should have backups.)
5. File locking / conflict handling.            5. No Locking; conflicts are less frequent.
6. Constant connection required.                6. Connection required only when sharing.
7. Defined workflow.                            7. Highly flexible workflows possible. With
8. Restricts free development of open source       subteams and sharing and merging before
   projects.                                       final publishing.
                                                8. Promotes Open Source development.
                                                                             @nikhilwanpal | NikhilWanpal


Slide 7: Understanding Git (coming from a world of CVCS)
● It is distributed: Things appear to be two step.
● Think of ‘torrents’, P2P networks. (It’s not a P2P and won’t help you download GOT!!)
● Like installing your own SVN server that can communicate with other SVNs.
● Branching is dirt cheap; not a task.
● Merging is easy; not an activity. (If you know what you are merging!)
● It’s not difficult, just different. (unless our glass is full)
                                                                      @nikhilwanpal | NikhilWanpal


Slide 8: Git Hosting
●  GitHub Vs GitLab Vs BitBucket
●  Git : GitHub = water : packaged drinking water
●  All hosting providers add proprietary features to git, ex: pull request.
●  Hosting providers do, can provide other VCS as well.
●  Git does not need hosting, or server or background process
●  Git can work with a shared folder as remote
●  Hosting makes corporate workflows easy
                                                                     @nikhilwanpal | NikhilWanpal


Slide 9: Your Git
● Install Git
● Setup
  git config --global user.name "Nikhil Wanpal"
  git config --global user.email "nikhil@dontwasteyourtimereading.com"
                                                                       @nikhilwanpal | NikhilWanpal


Slide 10: Your Git, Your First Repository
In a new directory: practical-git/1/
 ●   git init
 ●   Create file, git add, git commit -m
 ●   Modify file, git add, git commit -m
 ●   git log
 ●   Modify file, git add, git commit --amend
 ●   Modify file, git add
 ●   git reset
                                              @nikhilwanpal | NikhilWanpal


Slide 11: Your Git, Your First Repository with a server
In a directory: practical-git/central-repo.git/
      ●   git init --bare
In a directory: practical-git/personal-repo/
      ●   git clone ../central-repo.git/ .
      ●   git add
      ●   git commit -m
      ●   git push
                                                @nikhilwanpal | NikhilWanpal


Slide 12: Your Git, Your First Repository with a server and a
dual personality
In a directory: practical-git/central-repo.git/
      ●   git init --bare
In a directory: practical-git/personal-repo/
      ●   git clone ../central-repo.git/ .
      ●   Create file, git add, git commit -m
      ●   git push
                                                @nikhilwanpal | NikhilWanpal


Slide 13: Your Git, Your First Repository with a server and a
dual personality (v1)
In a directory: practical-git/colleague-repo/
      ●   git clone ../central-repo.git/ .
      ●   Surprise!
      ●   Create file, git add, git commit -m
      ●   git push
In a directory: practical-git/colleague-repo/
      ●   git pull
                                              @nikhilwanpal | NikhilWanpal


Slide 14: Branches and Tags
                  reviewComments
                  presentation4Team
                  V1
                  V1.1
                             @nikhilwanpal | NikhilWanpal


Slide 15: V1.1 Branches
● Threads of development
● String of thought
● Series of changes with similar purpose
● A diversion
  git branch myFirstBranch
● Create a file, git add, git commit -m, git push
  git checkout master
                                                  @nikhilwanpal | NikhilWanpal


Slide 16: V1.2 Merges
● Tie the threads together
● Bring together different thoughts and ideas
● Achieve the purpose of your branch
  git merge myFirstBranch
● Git’s intelligent merge
  git checkout myFirstBranch, modify line 1, push
  git checkout master, modify line 2, merge
                                                  @nikhilwanpal | NikhilWanpal


Slide 17: V1.3 Conflicts
● What happens when two different lines of thought try to merge?
● Branches need a judge!
● You!
  git checkout myFirstBranch, modify line 2, push
  git checkout master, modify line 2, merge!
● Now try that across repositories, you have 2.
                                                              @nikhilwanpal | NikhilWanpal


Slide 18: V1.4 Rebase
 ●   Rewriting history
(after same steps as a conflict..)
     git pull origin master --rebase
                                     @nikhilwanpal | NikhilWanpal


Slide 19: What is a:
● Git commits storage: a rooted, Directed Acyclic Graph of patches.
● Patch: the delta between two commits. (or more)
● Staging/Index: Selecting relevant changes for commit.
● Commit: The delta store in git filesystem with name as the SHA.
● Branch HEAD: A pointer in the graph for ease of access.
● Branch: The path from root to branch head.
● Stash: Stash aside the state for now.
● HEAD: a variable, a pointer to current pointer of the current branch.
● Detached HEAD: state of repository when a commit is checked-out, which is
  not pointed to by any of the HEADs
                                                                 @nikhilwanpal | NikhilWanpal


Slide 20: What is a:
● Merge: Delta from the ‘common ancestor’ added together.
● Fast - Forward Merge: Pointer updated to the latest head.
● Merge commit: the commit that identifies a merge.
● Rebase: Rewrite the history to change the branching point, and reapplying
  the changes over. No more the same commits. (creating new history is that easy..!)
● Reset: undo, hard vs soft.
● Remote: The different repositories, tracked branches, not same branches.
● Pull: fetch + merge (rebase!)
                                                              @nikhilwanpal | NikhilWanpal


Slide 21: Git Folders:
 ●   HEAD: pointer to current branch’s head
 ●   index: staging info
 ●   refs: commit objects. Basically branch data.
 ●   objects: blobs of files and tree objects.
Git Objects:
 ●   blobs: or git objects contain the contents of checked files. Key-value file
     storage.
 ●   trees: pointers to blobs by filenames and other trees.
 ●   Commit: top level tree, user, additional info regarding commit, message etc.
 ●   Packfiles and git gc | auto gc.
                                                                    @nikhilwanpal | NikhilWanpal


Slide 22: To Branch or not to branch..
What is a branch? (There is no such thing as a branch! It’s the path from the head to root,
traversed through ‘parent’ pointers.)
Git References:
       ○   Branches
       ○   Tags
       ○   HEAD
       ○   Remotes
Are you coming back to it? Then you need a branch!
                                                                            @nikhilwanpal | NikhilWanpal


Slide 23: Git Flow
●  A branching model suggested by Vincent Driessen in his blog.
●  develop and master: The only long lived branches.
●  Features, Releases and Hot-fixes
●  Convention: feature/; release/ and hotfix/
●  Life-cycle of:
    ○   Feature: develop → develop
    ○   Release: develop → (master + tag | develop)
    ○   HotFix: master → (develop + master(tag?))
                                                              @nikhilwanpal | NikhilWanpal


Slide 24: Git Shortcuts
Bash / shell aliases:        Git aliases:
 ●  alias gs='git status '    ●   git config --global alias.st status
 ●  alias ga='git add '       ●   git config --global alias.a add
 ●  alias gc='git commit'     ●   git config --global alias.ci commit
 ●  alias gb='git branch '    ●   git config --global alias.br branch
 ●  alias go='git checkout '  ●   git config --global alias.co checkout
                                                    @nikhilwanpal | NikhilWanpal


Slide 25: Git Best Practices
●  Commit often (every 30 mins), push once. Clean-up before push.
●  Prefer to code on new branch locally, never push such branches. Share
   among developers but not to central.
●  One change per commit. Not more.
●  Describe the commit well.
●  Consider rebase before push or pull, follow up with a --no-ff commit.
●  Don’t break the development tree.
●  Review merges. Build and fix post a merge before push.
●  Avoid force-delete (-D) when deleting branches.
●  Consider using shortcuts/aliases.
●  NEVER rebase pushed commits.
                                                                  @nikhilwanpal | NikhilWanpal


Slide 26: }
  @nikhilwanpal | NikhilWanpal

Using the link below, you can also download the PDF file for offline reference. Although, I prefer to revisit and update my presentations, you can always refer to the latest version here.

Where Do We Go Wrong With Agile

Where Do We Go Wrong With Agile

A few days ago I published this blog mocking the ‘Ceremony Focused Agile’ teams. But it is pointless to state what one thinks is not right, without also commenting on what one thinks is right! So let us do that today. Here is a conversation, which I am sure many of us have witnessed (or been part of):

A: “I have assigned a ticket to you, what is the status of it?”

B: “”Ticket, what ticket?”

A: “It’s in JIRA, check your board.”

B: “Okay, but what is it about?What is the context?”

A: “It’s in JIRA”

B: “huh?”

In Agile teams, people believe in using JIRA to track their work, hours spent, communication / discussion about a feature, proposed features, discarded features, its this amazing one-stop shop for all Agile stuff.. What a tool! (pun not intended!) We are told that using JIRA helps us track time, keeps everything organised, ensures no one can go back on their words or commitments. Which is true, using a single, capable tool for tracking everything related to a task would ensure that everything that happened in the context of a task. But let us not mistake using JIRA as practising Agile.

Agile Manifesto

Agile manifesto states in four, very clear and concise statements:

Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan

Yet, the reality is that these statements are understood by everyone differently. Some folks took away a different meaning from the word Agile itself, some did from the manifesto. Over time certain practices appeared, which seemed to work for certain use cases effectively. And many of us seem to have assumed their success is absolute, and expect them to work outside of the teams they were successful in. Somewhere we forgot, every team is different, so is agile for every team. It is certainly not a set of ‘mandatory rules’ that apply to every team the same way.

Then What Is Agile

AgilE to me is AtoE, or ‘Adapt to Evolve’. All the statements in the manifesto promise that when you change focus from tools/processes to people, from documentation to software, from contract to customer and form fixed plan to flexible plan, you will be able to evolve to match market needs and deliver a successful product. But then, how do we do it? Does it mean that we should stop using all tools/processes? Or signing contracts? Certainly not, these things are still important, but there is only so much that they can do. The manifesto tries to bring priority to them, stating that a doing is more important than planning, recording and tracking. That does not mean these are unimportant, but only that they are of less importance that the action itself.

When we put focus on people, and reduce the importance of processes and tools in the day to day life of these people, they interact more and better. This interaction results in better understanding and integration of the team itself. This results in better delivery. There is no tool that can match a person to person interaction. I understand, the interactions at times may not be face to face, but people have always communicated better when they talk than when they write. ‘Intent’ is always difficult to convey in writing, writing lacks tones. Also, these tools are asynchronous, adding further delays.

In the words Working Software, ‘working’ I believe is the important term. Working does not just mean ‘able to execute’, working means software fulfilling its purpose. A software is built to address a problem statement. As time passes the problem statement evolves, may be to adapt to the market, or to the changing landscape, or to fill a niche, but always with the intent of making solution more relevant. And hence the definition of ‘working’ keeps changing. And so the software should too. A Software is a way of specifying the requirements. This specification is a set of instructions, given to a machine to perform an algorithm, in a way that they can be clearly understood by others contributing to the specification. Also, if the software is supposed to replace the comprehensiveness of the documentation, without impacting the intended purpose of the documentation itself, then the same job must be done by the software equally well! In other words, the specification i.e. code, should read like a documentation! Now these, I believe constitute the ‘working’ of the software.

Engaging with the customer helps teams better understand their perspective which reflects in software. Contracts are required to ensure the business aspect of the software development, but they should not be a hindrance to value creation. The first and foremost job of an Agile team is to bring value to the customer, also referred to as Stakeholder. In the rawest of terms, it is more important to see if and how a task being done will bring value to the customer than looking for a way to create a new Change Request. 😉 Customers in software services industry are mostly external to the company or team and so collaboration becomes all the more important. In poetic terms, it is important to think of the software as ‘for us’ and not ‘for client’, and involving the customer aids this thinking.

It is a bit cliche to mention this, but ‘Change is the only constant’. There is no defined long term plan that can be executed exactly as expected, especially when the definition of ‘working’ itself is so prone to change. We can define a direction, and end goal, but we cannot define strict plan and even if we could, not sure it would help the changing context, except when ‘change is the plan’! Being able to incorporate change is the primary goal of an Agile team. Interestingly, when comparing different Agile frameworks you can see that one of the most important differentiating factor is the ‘frequency at which to expect change’. An Agile team should be ready and open to change than being strict about adhering to a plan. There are still plans, but in much smaller scale.

The Unsaid Requirements Of Agile

With all the points above, agile is said to give control to the team. An overused, always misunderstood term, “giving control”. And what does it mean? The ability to start or stop something, the ability to take decisions and executing them, that is control. Now I wonder, is it possible to give control, without having ‘trust‘? I do not see it possible, ever to do so. Would you ever give control of your car (project execution) to someone and ride along, without first trusting them to (intentionally or unintentionally) not kill you? Not possible. Traditionally, the management has always enjoyed this control. They have always believed that them making the decisions and team obeying and executing them is the right way. Agile requires them to relinquish this control, and it is certainly not going to be easy unless they trust the team to do the right thing.

So, the ‘management’ of an Agile team needs to first trust the team.

Now, would you trust a driver with no driving skill? Nope! The team needs to have the skill to make right choices, execute and deliver. Without this skill it is not possible for the management to trust the team. and without trust it is not possible for a team to be Agile.

An Agile team needs to have the required skill-set to make the project a success.

Would you trust a skilled, but irresponsible driver with your car and life? Would you trust a skilled, responsible yet unwilling driver, to take you to your destination? Certainly not, you and your car might end up in a ditch with the driver unscathed will move on to drive a different car! (analogy!) It is irrelevant if the driver is skilled, unless the driver is willing to take you to your destination, her skills are useless. The goals must align.

An Agile team must believe in the same goal as the management, must be willing to do what is needed to get there.

I always see the last requirement as a bit tricky. Why would a team of skilled, free-thinking individuals believe in someone else’s goal? This is where the ‘people interactions’ come in. It is not going to happen unless the team trusts the management to do right by them. Ah, it’s a game of trust, skill and will. There is no Agile without these. These assumptions should have been recorded somewhere, because this is the part that many teams and many traditional managers fail to understand. What this results into is a ceremony we like to call Agile.

The Ceremony

There are many ‘frameworks’ of Agile. Many different ways that can help you implement the manifesto better and they have different guidelines, like all thought-processes do. But these are guidelines, not rules. They cannot be forced on an unwilling team to beat them into being Agile. The core concept of Agile is that the team decides the practices they want to follow, in which form, to identify flows and improve on them. (Remember, we have already trust that the team is skilled and is willing to do right by this project.)

When we see meetings, call timings and statements forced upon team, they become mere ceremony, they lose their meaning, purpose and the result is a failure. A failure to achieve the goal, failure to build the team and a failure of the practice itself.

There are certain tools and practices though, that explained as being a part of Agile. These again are not rules, but arise from the need to respond to change rapidly. We need to deliver fast, and to do that. we need faster verification of software hence the need for Continuous Integration. To be able to deploy fast we need Continuous Delivery, so the artefacts are ready to go live, daring teams can even try Continuous Deployments. To deploy fast, we need to make the provisioning and configuration of systems automated and simplified, hence the need for DevOps. A car can go only as fast as the breaks can allow, so to deliver fast we also need to be able to revert fast, hence the need for artefact repositories and blue-green deployments. We need to change the specification quickly and hence the need to verify the specification at granular level, hence the need for Unit Tests. Since we are so focused on time, we should write specifications only for what is required, hence the TDD/BDD. Since the specification’s job is to convey intent to others, we need to have more than one person on the team who can understand the code, and to save time and effort, we have Pair Programming. Again, just following such does not make you Agile, similar to how not following some of them does not make you ‘not Agile’. Using Jenkins/GoCd, JIRA, Artifactory/Nexus etc tools does not make you Agile, and not using them, for a better alternative your team has established which allows you to act faster, does not make you ‘less Agile’.

And many other terminologies you would hear in Agile, know that are not part of the specification or requirement or some rule. Some of these things may help you be Agile, but the Agility is always in the context of what your team thinks is necessary to achieve the goal for your Customers.

The Markers

Enough theory, how do I tell if my team is Agile? Well, I have tried to build a list of markers that I have seen in non-agile Agile teams. Now this is certainly not an exhaustive list, and it is certainly not a rule, but indicators that can help identify the ceremony than agility.

  • You have a “manager”.
  • Your manager/scrum master, or someone ‘assigns’ you ‘tasks’, rather than you picking them.
  • This someone asks you for ‘status’ in your daily meetings. This is a bit tricky, remember you have control, and so you have responsibility to convey the status of the work you picked. It might be a failure on your side or management’s.
  • If your team has members reporting to different people, not in hierarchy.
  • If you learn about your tasks only via a tool, and also report via a tool.
  • If you prefer a tool or email over talking/quick calls when you need to discuss with your team.
  • If you have to jump through hoops and cc ten people to be able to talk to the customers.
  • If your productivity is measured solely in terms of ‘tickets’ fixed or moved.
  • If you as a team never meet to discuss what can be improved or you conclude that nothing can be!
  • If you do not know what others in your team are working on, blocked on and you are not helping to unblock them.
  • If you as a team are not driving to complete the goal of the iteration as a whole, and instead focus on finishing your work alone.
  • If you as an individual are not learning any new skill required by your work or performed in the team.
  • You have not changed the way you are working / following Agile practices in a long long time!

 

[TechNggets] Episode 2: Intro to Git Flow

[TechNggets] Episode 2: Intro to Git Flow

This is the second episode of podcast “Tech Nuggets and Thoughts”.

 

Some docs on git flow:

  1. The blog that brought it to us: http://nvie.com/posts/a-successful-git-branching-model/
  2. git flow scripts project discussed in podcast: https://github.com/petervanderdoes/gitflow-avh
  3. A superb cheat sheet for git flow: https://danielkummer.github.io/git-flow-cheatsheet/

 

To get updates, you can subscribe to the podcast on: Apple iTunesplayer.fmRSS feed. If you have any suggestions, thoughts or recommendations, please feel free to comment below. You can also reach me on podcast’s twitter handle @TechNggets or my personal account @nikhilwanpal.

(If the fancy player above does not work, try the bare bones player below.)