GIT Basic usage

This tutorial walks through basic GIT usage in the local directory.
The tutorial covers:

.
• How to intiailise a directory to make it a git repository.
• How to add and commit any new files or changes to files, to the change history.
• How to view the status of the repository and look at its history in various ways.
• How to make a branch in the master branch to allow new versions to be developed.
• How to merge any development versions back into the master version.
• Understanding of how conflicts are created and how to solve them.
• How to revert to an earlier version of a project and resolve any conflicts.

Contents

• Git initialisation
• Git commit
• Git branch
• Git merge
• Git revert

Instructions are in blue,
commands to be typed are in a bordered white box
and a 'Return' should be made after each instruction.
The terminal output is in a bordered yellow box
and webpage edits are in a bordered blue box

Creating the repository

To create a git repository the directory in which you want to track changes.
The first step is to initialise the directory and save any files present using the git commit method.

Begin by creating a new directory an changing into it.

mkdir git-demo
cd git-demo

Create a README.txt as recommended by GIT

echo This is a demonstration of basic git operations > README.txt

Check file is there

ls -al

Initialise this directory as a git directory.

git init

Initialised empty Git repository in .../git-demo/.git/

See the status of the new directory

git status

To 'Stage' the file ready for 'Saving' to the repository we use 'git add', as suggested:

git add README.txt

...and to 'save' the 'staged' file(s) into repository

git commit -m 'first commit'

Note: The commit numbers will be different on your machine.

See the status of the repository

git status

Copy and paste the following into a new text file and save as webpage.html
in the git-demo directory created earlier.

See the status of the repository

git status

'Stage' the file ready for 'Saving' to the repository using 'git add', as suggested:

git add webpage.html

As before commit the changes using 'git commit'

git commit -m 'Version 1 of webpage'

Edit webpage.html. Change 'version 1' to read as 'version 2'and save.

version 2 on

See the status of the repository

git status

'Stage' the file ready for 'Saving' to the repository using 'git add', as suggested:

git add webpage.html

As before commit the changes using 'git commit'

git commit -m 'Version 2 of webpage'

See the status of the repository

git status

Edit webpage.html. Change 'version 2' to read as 'version 3' and save.

version 3 on

See the status of the repository

git status

'Stage' the file ready for 'Saving' to the repository using 'git add', as suggested:

git add webpage.html

As before commit the changes using 'git commit'

git commit -m 'Version 3 of webpage'

Exploring the history Git Log

Enter git log

git log

Press SHIFT and Q to quit the readout or RETURN to move down the list

The output can be modified with git log options: enter

git log --oneline

And the output can be in the form of a primitive graph: enter

git log --graph

And mixed together: enter

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

It is useful to have the last command an alias to save the typing: enter

Linux: alias gitgraph='git log --oneline --graph --decorate --all'

Windows: Function gitgraph { git log --oneline --graph --decorate --all}

Now typing gitgraph will display as before: enter

gitgraph

Exploring the differences: Git Diff

Enter git diff with the Version 2 commit id , then the Version3 commit id.

git diff 939e01c e731947

Branching

Safe modifications to version edits

Enter git branch new_version

git branch new_version

Now look at all the branches: enter

git branch

To use the branch we must switch to it:

git checkout new_version

Reopen the file webpage.html and change as follows and save

To save the changes on the new branch, add and commit the changes

git add webpage.html

git commit -m 'version 4 on branch new_version'

Now use gitgraph to see the changes

gitgraph

The HEAD is now set to new_version.To see the effect refresh webpage.html in the browser

To see Version 3 again we need to switch back to master:

git checkout master

The HEAD is now set to master. Refresh webpage.html in the browser

Switch back to new_version:

git checkout new_version

Now make one more version of webpage.html
Change and save the version line to read as follows:

<span class="mydivstyle">This is <b>version 5</b> on

After saving webpage.html, add and commit changes:

git add webpage.html

git commit -m 'version 5 on branch new_version'

Now use gitgraph to see the changes

gitgraph

Merging branches

Change back to master branch

git checkout master

Should you decide that you like the changes made to new_version
and want to make them part of the master branch.

The format of the merge command is git merge <source branch> <target branch>
Source and Target are optional - if you only have one branch you do not need to specify
Perform git merges from the master branch.

git merge new_version

Now use gitgraph to see the changes

gitgraph

Refresh webpage.html and you will see that the colour has changed to pink and the version number has changed to 5.
and the branch has changed the 'new_version'.

Conflicts

Sometimes you will get conflicts: this happens when a branch version has had the same line(s) altered as on the master branch.
When GIT tries to merge it does not know which change should take priority.

Change webpage.html to lines to read as "version 6 and "new_version" to "master", as before in the text editor.

After saving webpage.html, add and commit changes:

git add webpage.html

git commit -m 'version 6 on branch master'

Change back to new_version branch. Change the version number to 7 for webpage,html, as before in the text editor.

git checkout new_version

After saving webpage.html, add and commit changes:

git add webpage.html

git commit -m 'version 7 on branch new_version'

Change back to the master. Now try a git merge:

git checkout master
git merge new_version

Now look at the file in the text editor. You will see that git has highlighted the problem line(s)