Git

Published: Fri 12 June 2020
By Alex

In misc.

Intro

To begin with you'll need to have a computer to store a folder with content (local repo). After you are happy with you content you can 'send' it to remote repo. Sometimes it is vice versa from remote you get some code into your computer. Anyway computer and github account can be conected that is why I write all this article noise. I am born 1988 and use internet since 2007 daily and getting github account (around year 2017) is the best thing happened to me on the Internet.

Git Basics

Great ressource to start with is the codecademy.com where most of the examples here are pulled from: https://www.codecademy.com/learn/learn-git

Cheatsheet

git branch: Lists all a Git project’s branches.
git branch branch_name: Creates a new branch.
git checkout branch_name: Used to switch from one branch to another.
git merge branch_name: Used to join file changes from one branch to another. (branch_name is a giver branch)
git branch -d branch_name: Deletes the branch specified.
giver branch receiver branch

Setup and First commit

  ______________
||             ||
||             ||
|| C:\here\.git||  --> <https://github.com/thisAKcode/here>
||             ||
||_____________||           
|_______________|
 \\#############\\
  \\#############\\
   \      _____    \   
    \_____\____\____\    
 ```   
 LOCAL repository > REMOTE repository

C:\here    --> https://github.com/thisAKcode/here

### Initial Setup
`git config --global user.name "thisAKcode"`

`git config --global user.email "alekseikupiakov@hotmail.com`

To set up Git username and email you can check github documentation:

<https://docs.github.com/en/github/getting-started-with-github/set-up-git>

<https://docs.github.com/en/github/setting-up-and-managing-your-github-user-account/setting-your-commit-email-address>

### HTTPS | SSH
GitHub offers two authentication options, HTTPS and SSH.
I use HTTPS. There is an article on caching your password to configure your computer to be able to [use HTTPS](https://docs.github.com/en/github/using-git/caching-your-github-credentials-in-git).

### Making First Commit! 
Commit is a command that executed at the end of writing.
```bash
mkdir git_practice
cd git_practice
git init 
echo "Hello Git and GitHub" >> README.txt
git add README.txt
git commit -m "First commit"

Type git status to check new or edited files and folders.

Link GitHub repo to local Git repo

  1. Create remote repo on GitHub named /here.git.
  2. Push an existing repository from the command line
git remote add origin https://github.com/thisAKcode/Git.git
git push -u origin master

If it is first time you are prompted for username and password The push is complete after the above command executed succesfully.

Backtracking

Different ways to backtrack in git:

git checkout HEAD filename: Discards changes in the working directory.
git reset HEAD filename: Unstages file changes in the staging area.
git reset commit_SHA: Resets to a previous commit in your commit history.

Eraser features

How do I get rid of some changes that were made? Imagine scenario: I create a file in a working directory. I add some initital content ("... enikibeniki") to it : vim myfile.txt

here is my original content
Here I have to add bogus on the next line.
"enikibeniki"

I add changed file to staging area then commit

git add myfile.txt
git commit -m "added some bogus"

Now myfile looks like that cat myfile.txt

here is my original content
Here I have o add bogus on the next line.
"enikibeniki"

Head Commit

You are currently on commit that is called HEAD. HEAD is at the most recent commit To check HEAD: git show HEAD

commit f33412218ee787f149e41f6d8d9d2d25a50ec190 (HEAD -> master)
Author: AKcode <43783718+thisAKcode@users.noreply.github.com>
Date:   Fri Mar 12 14:57:41 2021 +0100

    added some bogus

diff --git a/myfile.txt b/myfile.txt
new file mode 100644
index 0000000..9784014
--- /dev/null
+++ b/myfile.txt
@@ -0,0 +1,3 @@
+here is my original content
+Here I have to add bogus on the next line:
+"enikibeniki"

Edit and Call git diff to Inspect Changes

` I change the last line in the working directory adding some extra chars.

here is my original content
Here I have to add bogus on the next line.
"enikibeniki" and "elivareniki"

git diff results in: 

warning: LF will be replaced by CRLF in myfile.txt.
The file will have its original line endings in your working directory
diff --git a/myfile.txt b/myfile.txt
index 9784014..7e3c898 100644
--- a/myfile.txt
+++ b/myfile.txt
@@ -1,3 +1,3 @@
 here is my original content
 Here I have to add bogus on the next line:
-"enikibeniki"
+"enikibeniki" and "elivareniki"

Scenario: Suddenly I Change My Mind

Then I decided to discard added chars and "elivareniki". In a working directory I want to get my file look as it was before and "elivareniki" insert . git checkout HEAD myfile.txt Changes made to myfile.txt will be gone. Most recently-committed version of the file overwrite your current copy. So you get back your thing, and to prove than do git show HEAD

+here is my original content
+Here I have to add bogus on the next line:
+"enikibeniki"

sweet!

More on git add

It is possible to add to the staging area, and commit them to a repository in a single commit. 

git add file_1 file_2
git commit -m "try to commit 2 things"

git reset I

Think if you in file_2 did delete an important line. Unstage that file from the staging area using git reset HEAD file_2 It doesn't affect on working directory, but removes changes from the staging area. M file_2 M is short for “modification” git commit rectified

git reset II

When you get lost in your commits you can rewind the part to before you got confused. Print out git commit log git log, press “q” to escape.

Choose the previous commit from list of past commits.

git reset commit_SHA using 7 characters of SHA.

git reset 1a232456 The characters are hexadecimal digits (0-9, a-f)

HEAD goes to commit of your choice. Commits after reset are not part of your project anymore.

Practice Backtracking

To discard changes and restore a fiel in the working directory, do checkout HEAD version of file1 as per last commit: git checkout HEAD file1 or use common shortcut: git checkout -- filename. Close and re-open the file1 to see the result. Restored and completed file1 has to be added to the staging area along with two files file2 and file3.

Practice Unstage file1 After git add ..

Unstage & then continue commit files that you consider okay to commit 

git reset HEAD file1
git commit -m "files good to go

Practice Regret My Last Commit

Here is commit I edit After git add. && git commit -m "my message" I decided to rollback. git reset d1fc1f2 Here’s a problem: reset HEAD to a previous commit, but the changes persist in the working directory. Git backtracking command that you already know can discard changes to the working directory

git checkout HEAD file1.txt

Yeah!

Practice Reset

You have some content in the last commit that was deleted in the working directory. To get that back, discard changes in the working directory for file_x.txt

git reset file_x.txt
git checkout -- file_x.txt

...then edit file and add the file to the stagin area

git add file_x.txt && git commit -m "changes to file_x" ... then you come up with idea that you forgot add signature

NOTE

add . is used broadly but make sure you always know what you’re adding.

Remove the File From Staging Commit

Add 3 files to the staging area git add file_x.txt file_y.txt file_z.txt Unstage file_z.txt from a staging area git reset HEAD file_z.txt continue commit git commit -m "all files commited except file_z.txt"

Backtrack

The purpose of Git backtracking commands: discard changes in working directory go back to a previous commit unstage file from a staging area To achieve it you type: git log to view the SHAs of all previous commits. git reset HEAD filename removes file changes from the staging area and reports undtaged changes after reset.

Undo Accidentally Deleted Lines

git checkout HEAD filename rewind accinentally edited changes

reset HEAD to a commit with this SHA

git reset 844d1f7

NOTE What is HEAD commit? Commit you are currently on.

A New Project Feature - a New Branch

At the point of creating a new branch, new branch and "master" share the exact same commit history, then you develop multiple versions of a project. git branch check branch, result shows what branch you're on.

      nb-nb
     /
mb-mb-mb-mb

New branch is a new version of the Git project: new branch contains commits from master but also own unique commits. git branch new_branch creates new branch while staying on master. git checkout new_branch switch to the branch, work, while master stays intact.

git merge

Git merge executed to update master: include all the changes from the fencing branch to the master branch. git merge branch_name merge branch_name to master

branch_name is the giver branch(provides the changes). master is a receiver branch since it accepts those changes.

NOTE

branch_name is the giver branch(provides the changes).

master is a receiver branch since it accepts those changes.

Scenario Merge Two Branches

What if I decided to switch back to master then ask Git to merge the two branches

merging the branch into master

From the terminal, merge the fencing branch into the master branch. git merge branch_name Output says it is fast-forward. Git recognizes that branch_name contains the most recent commit. Git fast forwards master to be up to date with branch_name.

Merge Conflict I

Merge works fine where master has no changes since commit on branch_name. merge conflict I commit on branch_name plus commit on master before you merge the two branches. Git cannot decide for you which changes you want to keep.

Merge Conflict II

You’ve made commits on separate branches that alter the same line in conflicting ways. The trouble begins! In case of merge Git need help to know which version of the file to keep.

Fix The Merge Conflict

in the file concerned you see the changes that made it impossible to merge.

<<<<<<< HEAD
-Lorem ipsum dolor sit amet 
=======
-Lorem ipsum dolor sit amet such as pain.
>>>>>>> branch_name

interpret marks in concerned text

Git need to have properly distinguished which version of the file to keep: on master or on branch-name. If I decide to keep changes according to branch-name I delete line as per master, all of Git's special markings including HEAD and branch_name. Then add and commit file git add filename.txt && git commit -m "test".

Delete Branch

In Git the branch has to be merged to the master branch at the end, after not master branch served its purpose it can be deleted: git branch -d branch_name

Merge conflict

<<<<<<< 

HEAD -
 Intuitive and easy to use, providing crucial functionality 
======= 
- Intuitive and fun for use, offering the best in software 
>>>>>>> feature

While on master merge the edits branch into the master branch. git merge edits as a result you got two merge conflicts: README.md and examples.md.

Git Teamwork

A suite of collaboration tools. I am a collaborator. Work with Bob.

Remote is Needed

To work together the following required: 1. Complete replica of the project on your own computers. 2. Way to keep track of and review each others work. 3. access to a definitive project version.

Git clone

git clone remote_location clone_name where remote_location could be web adress or a filepath and where clone_name is the name you give to directory-destination for your clone.

Remote Adress is origin

git remote -v lists Git project's remotes (origin by default) and its location

Git fetch

What if your collaborator changed the content. If so, your clone will no longer be up-to-date.

Me Doing Slow Fast-forwards

I cannot remember scenario, but I used to do some troubleshooting of git push origin master.

(venv) λ git push origin master
To https://github.com/thisAKcode/thisAKcode.github.io.git
 ! [rejected]        master -> master (non-fast-forward)

error: failed to push some refs to 'https://github.com/thisAKcode/thisAKcode.github.io.git'
hint: Updates were rejected because a pushed branch tip is behind its remote
hint: counterpart. Check out this branch and integrate the remote changes
hint: (e.g. 'git pull ...') before pushing again.

hint: See the 'Note about fast-forwards' in 'git push --help' for details.

Reverting Commit

After doing push my pelican site died and I needed the way to get thing back as they were just before. For whathever reason I am evey now and then reverting to a specific commit based on commit id with Git.

Undo a whole commit with all changes instead of going through all the changes manually git has stuff to revert a commit, which does not even have to be the last one. "Reverting a commit means to create a new commit that undoes all changes that were made in the bad commit. Just like above, the bad commit remains there, but it no longer affects the the current master and any future commits on top of it." https://opensource.com/article/18/6/git-reset-revert-rebase-commands https://git-scm.com/docs/git-revert https://github.com/git/git/blob/master/Documentation/howto/revert-a-faulty-merge.txt

Screw it: Practice makes perfect

I'll say it again!

Ressources

https://happygitwithr.com/push-rejected.html https://happygitwithr.com/pull-tricky.html https://ohshitgit.com/

links

social