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PROJECT MANAGEMENT (WITH GIT)

1BCSL307A

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Experiment 2 - Creating and Managing Branches:

Create a new branch named "feature-branch." Switch to the "master" branch. Merge the "feature-branch" into "master."

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Git Branching

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BRANCHING IN VCS

Branching means you diverge from the main line of development
continue to do work without messing with that main line
Other VCS Tools – an expensive process requiring copy of source code directory
Git Branches – lightweight
Git stores data as snapshots NOT differences.

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COMMIT AND ITS TREE

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Git stores a commit object that contains a pointer to the snapshot of the content you staged
object also contains the author’s name and email address, the message that you typed, and pointers to the commit or commits that directly came before this commit
zero parents for the initial commit

one parent for a normal commit
Multiple parents for a commit

that results from a merge of

two or more branches

$ git add README test.rb LICENSE

$ git commit -m 'Initial commit'

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BRANCH IN GIT

If you make some changes and commit again, the next commit stores a pointer to the commit that came immediately before it.
A branch in Git is simply a lightweight movable pointer to one of these commits
default branch name in Git is master or main. It gets created on git init
Every time you commit, the master branch pointer moves forward

automatically.

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BRANCH AND ITS COMMIT HISTORY

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CREATING A NEW BRANCH

creates a new pointer to the same commit you’re currently on.
special pointer called HEAD
In Git, this is a pointer to the local branch you’re currently on
Notice it is still on main
To switch to an existing branch, use git checkout

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hp-pc@ projects/flask-git-lab (main)

$ git branch --show-current

main

hp-pc@projects/flask-git-lab (main)

$ git branch testing

flask-git-lab (main)

hp-pc@projects/flask-git-lab (main)

$ git log --oneline --decorate

3b4e9e3 (HEAD -> main, origin/main, testing) update readme

535806a Initial flask application

hp-pc@projects/flask-git-lab (main)

$ git checkout testing

Switched to branch 'testing’

hp-pc@projects/flask-git-lab (testing)

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SWITCHING TO A NEW BRANCH

branch in Git is actually a simple file that contains the 40 character SHA-1 checksum of the commit it points to
branches are cheap to create and destroy
older VCS tools –copies everything into a second directory.
From Git version 2.23 onwards you can use git switch instead of git checkout
Switch to an existing branch: git switch testing-branch.
Create a new branch and switch to it:

git switch -c new-branch.
-c flag stands for create, you can also use the full flag: --create.
Return to previous branch : git switch -.

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hp-pc@projects/flask-git-lab (testing)

$ vim test.txt

hp-pc@projects/flask-git-lab (testing)

$ git add test.txt

hp-pc@projects/flask-git-lab (testing)

$ git commit -a -m 'Make other changes'

[testing 5df08dd] Make other changes

1 file changed, 1 insertion(+)

create mode 100644 test.txt

hp-pc@projects/flask-git-lab (testing)

$ git log --oneline --decorate --graph --all

* 5df08dd (HEAD -> testing) Make other changes

* 3b4e9e3 (origin/main, main) update readme

* 535806a Initial flask application

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BASIC BRANCHING AND MERGING

1. Do some work on a website.

2. Create a branch for a new user story you’re working on.

3. Do some work in that branch.

At this stage, you’ll receive a call that another issue is critical and you need a hotfix. You’ll do the following:

1. Switch to your production branch.

2. Create a branch to add the hotfix.

3. After it’s tested, merge the hotfix branch, and push to production.

4. Switch back to your original user story and continue working.

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Assume some commits on master
Then switch to iss53
$ git checkout -b iss53

Change a file

git commit -a -m 'Create new footer [issue 53]'

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BRANCHING AND MERGING

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Switch back to master
$ git checkout master
if your working directory or staging area has uncommitted changes that conflict with the branch you’re checking out, Git won’t let you switch branches
best to have a clean working state when you switch branches
stashing and commit amending
your project working directory is exactly the way it was before you started working on issue #53
Git resets your working directory to look like it did the last time you committed on that branch
adds, removes, and modifies files automatically to make sure your working copy is what the branch looked like on your last commit to it.

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BRANCHING AND MERGING

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Make the hotfix
$ git checkout -b hotfix

Make changes to files

$ git commit -a -m 'Fix broken email address‘
Run tests, merge it back to master
$ git checkout master
$ git merge hotfix
This results in “fast-forward” in that merge
commit C4 pointed to by thebranch hotfix you merged in was directly ahead of the commit C2 you’re on, Git simply moves the pointer forward.

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BRANCHING AND MERGING

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Switch back to the work you were doing
$ git branch -d hotfix
Delete the hotfix branch
Now the work you did in hotfix branch will not be in the iss53 branch.
Now merge again
$ git checkout master
$ git merge iss53
In this case, your development history has diverged from some older point.
Git does a simple three-way merge, using the two snapshots pointed to by the branch tips and the common ancestor of the two.

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BRANCHING AND MERGING

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Instead of just moving the branch pointer forward
Git creates a new snapshot that results from this three-way merge and
automatically creates a new commit that points to it.
This is referred to as a merge commit, and is special in that it has more than one parent.
Now close the iss53 branch
$ git branch -d iss53

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BRANCHING AND MERGING

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Exp 2 - Git Branching

Set up configurations - user name, email, defaultBranch - set to master
Go to HOME folder, create directory, branchUSN
Change to directory
Create README.md app.py requirements.txt
Initialize git
Stage and do initial commit
Perform another 2 commits for C1(update readme, C2 (update app)

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Git Branching

1. Create a feature-branch

2. Switch to feature-branch

3. Create / update files

4. Stage and commit (C3 -commit)

5. Switch back to master branch

6. Merge feature-branch with master branch

7. print log, branches

8. Delete the feature-branch.

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MERGE CONFLICTS

If you changed the same part of the same file differently in the two branches you’re merging, Git won’t be able to merge them cleanly
Run git status to check which files are unmerged
Git adds standard conflict-resolution markers to the files that have conflicts
After you’ve resolved each of these sections in each conflicted file, run git add on each file to mark it as resolved

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hp-pc@myflaskapp (master)
$ git merge feature
Auto-merging README.md
CONFLICT (content): Merge conflict in README.md
Automatic merge failed; fix conflicts and then commit the result.

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BRANCH COMMANDS

get a simple listing of your current branches

$ git branch

To see the last commit on each branch

git branch -v

To see which branches are already merged into the branch you’re on

$ git branch --merged

To delete branch

$ git branch -d testing
Will fail if it is not fully merged

To rename a branch

$ git branch --move bad-branch-name corrected-branch-name

To rename at remote

$ git push --set-upstream origin corrected-branch-name

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Experiment 2 - Creating and Managing Branches:

Create a new branch named "feature-branch." Switch to the "master" branch. Merge the "feature-branch" into "master."

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STEPS

Assume you need to add a recommendations feature using a new file named recommendations.html.
Ensure you’re inside your flaskapp
Rename your main branch to master
Create a new branch named feature-branch.
Add recommendations.html.
Commit the feature.
Switch to the master branch.
Merge feature-branch into master.

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VIVA

1. Which command creates a new branch and switches to it?

A)git branch new-branch

B) git switch -c new-branch

C) git merge new-branch

D) git commit -b new-branch

2. Which command merges feature-branch into main?

git merge main
git branch feature-branch
git merge feature-branch
git switch feature-branch

3. The command used to create a new branch is __________.

4. The command used to switch to the main branch is __________.

5. What is the purpose of creating a separate feature branch in Git?

6. Which command is used to delete a merged branch?

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VIVA - ANSWERS

git switch -c new-branch
git merge feature-branch
git branch branch-name
git switch main
To develop features independently without directly affecting the main branch.
git branch -d branch-name

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