Quickstart: Git

Introduction

A distributed revision control system
Doesn’t require a central server to work
Download at: http://git-scm.com/
Command line tutorial below, execute code blocks in sequence
Lines starting with # are command line outputs or notes
Available on GitHub CornerGeeks/test-git

Configuration

git config --global user.name "John Doe"
git config --global user.email johndoe@example.com
git config --list

# user.name=John Doe
# user.email=johndoe@example.com
# -- other config

git config user.name

# John Doe

user.name and user.email is what is recorded in commit logs

Initialise

Go to a folder in command line and initialise it as a git repository

git init

# # Initialized empty Git repository in /Users/user/test_git/.git/

See current status and branch

git status

# # On branch master
# #
# # Initial commit
# #
# nothing to commit (create/copy files and use "git add" to track)

Will show current branch and status of files in the folder

Save (Commit) files into the Repo

Create a file & add it to the staging area
```
touch README
git add README
```

See current status

git status

# # On branch master
# #
# # Initial commit
# #
# # Changes to be committed:
# #   (use "git rm --cached <file>..." to unstage)
# #
# #    new file:   a
# #

Commit the file

git commit -m "Added README (C1)"

# [master (root-commit) 93ecaa8] Added README (C1)
#  1 file changed, 0 insertions(+), 0 deletions(-)
#  create mode 100644 README

Can also commit with “git commit” then type in the editor and save

Status of Files

Untracked: Will not be saved / commited into the repo (“git add filename” to stage”)
Staged: To be saved into the repo (“git commit” to save into repo and make it unmodified)
Unmodified: Previously committed. Currently has no changes
Modified: Previously committed. Content has changed. Stage file (“git add filename”) in order to commit new version to repo

Cannot commit empty folders into git

Staging Files

A file needs to be staged before it can be committed

A staged file will stage the file at that point in time

git status

  # # On branch master
  # nothing to commit, working directory clean 

echo "line 1" >> README
git status      

  # # On branch master
  # # Changes not staged for commit:
  # #   (use "git add <file>..." to update what will be committed)
  # #   (use "git checkout -- <file>..." to discard changes in working directory)
  # #
  # #    modified:   README
  # #
  # no changes added to commit (use "git add" and/or "git commit -a")

git add README
echo "line 2" >> README
git commit -m "commits only line 1 (C2)"

   # [master 58001d6] commits only line 1 (C2)
   #  1 file changed, 1 insertion(+)      

git status

  # # On branch master
  # # Changes not staged for commit:
  # #   (use "git add <file>..." to update what will be committed)
  # #   (use "git checkout -- <file>..." to discard changes in working directory)
  # #
  # #    modified:   README
  # #
  # no changes added to commit (use "git add" and/or "git commit -a")      

git commit -am "auto stage tracked files and commit (C3)"

   # [master cbf5a24] auto stage tracked files and commit (C3)
   #  1 file changed, 1 insertion(+)

Viewing previous commit logs

git log
git log -2
git log --pretty=oneline
git log --pretty="format:%h: %s (%an)"

See previous commit states

-Checkout the state of the repo at any commit

# git checkout previousCommitHashShownInGitLog

git log --pretty=oneline

  # cbf5a24f41bb8a2f70527f5a96cea4fca411910b auto stage tracked files and commit (C3)
  # 58001d6d9c474a6e5b102cf53a1948b0f5fd213d commits only line 1 (C2)
  # 93ecaa8c1238b872827781f6136401e4b9e3849b Added README (C1)

cat README

  # line 1
  # line 2

git checkout 25555caa7589363b20b3e1b34bd7ba979c13ff57
cat README

  # line 1

git checkout master
cat README

  # line 1
  # line 2

Think of commits as chain of events linked to the previous commit
```
C1 - C2 - C3 <-- master <-- head
```
master is the default branch and points to the last commit in the branch
HEAD points to you current location in the commit chain (changes when you checkout)
Checking out will move the head pointer and shows the state of the files at the point in time
“git checkout master” will point the HEAD back to master which is the latest commit
Note: All version of files are stored locally so you can git checkout without any network

Ignoring Files

Specify in .gitignore folder

touch ignore_this_file
git status
  # # On branch master
  # # Untracked files:
  # #   (use "git add <file>..." to include in what will be committed)
  # #
  # #    ignore_this_file
  # nothing added to commit but untracked files present (use "git add" to track)

echo "ignore_this_file" >> .gitignore
git status
  # # On branch master
  # # Untracked files:
  # #   (use "git add <file>..." to include in what will be committed)
  # #
  # #    .gitignore

Branches

When working on a new feature, create a feature branch, work on it and then merge it into the master branch

View Branches

git branch
    # * master

    # C1 - C2 - C3 <-- master <-- head

Create New Branch

git branch new_feature
    # C1 - C2 - C3 <-- master <-- head
    #           ^
    #           '---- new_feature

git branch
    # * master
    #   new_feature

Switch to new branch

git checkout new_feature
    # Switched to branch 'new_feature'

    # C1 - C2 - C3 <-- master
    #           ^
    #           '---- new_feature <-- head

git branch
    #   master
    # * new_feature

echo "new feature" >> README

git commit -am "new feature added (C4)"          

   # C1 - C2 - C3 <-- master
   #           |
   #           '---- C4 <-- new_feature <-- head

Merging Branches

Merge changes from new_feature into master

git checkout master

  # C1 - C2 - C3 <-- master <-- head
  #           |
  #           '- C4 <-- new_feature

git merge new_feature master
  # Updating e7578b4..13107de
  # Fast-forward
  #  README | 1 +
  #  1 file changed, 1 insertion(+)

  # C1 - C2 - C3 
  #           |
  #           '- C4 <-- new_feature 
  #               ^
  #               '---- master <-- head

As master has not been changed, the master pointer just “fast forwards”

Delete Branch after use

git branch -d new_feature

    # C1 - C2 - C3
    #           |
    #           '- C4
    #               ^
    #               '---- master <-- head

Merge Conflicts

Happens when conflicting changes happen between merges
```
  C1 - C2 - C3 - C4 <-- master
```

Create new branch and switch to it (shortcut)

git checkout -b merge_conflict

echo "merge_conflict_branch" > README
git commit -am "one line README in merge_conflict (C5)"

  # C1 - C2 - C3 - C4 <-- master
  #                |
  #                C5 <-- merge_conflict  <-- head

git checkout master
echo "master add new line" >> README
git commit -am "yet another line (C6)"

  # C1 - C2 - C3 - C4 - C6 <-- master  <-- head
  #                |
  #                C5 <-- merge_conflict

git merge merge_conflict master

  # Auto-merging README
  # CONFLICT (content): Merge conflict in README
  # Automatic merge failed; fix conflicts and then commit the result.

Will now need to edit the README file manually to resolve conflicts

 cat README

   # <<<<<<< HEAD
   #  line 1
   #  line 2
   #  new feature
   #  master add new line
   #  =======
   #  merge_conflict_branch
   #  >>>>>>> merge_conflict

New file shows the changes between the branches.
Delete and clean the <<<<<<, =======, >>>>>> and text in between.
- “<<<<<<<” : start of your current branch’s file
- “=======” : end of your current branch’s file & start of the difference from other (merged) branch changes
- “>>>>>>>” : end of other branch changesgit commit -am “merged merge_conflict with master (C7)”
```
 # C1 - C2 - C3 - C4 - C6 -C7 <-- master  <-- head
 #                |
 #                C5 <-- merge_conflict
```

Show changes

Changes that haven’t been staged

echo "diff me" >> README
git diff

  # diff --git a/README b/README
  # index 4b7c1e3..f6a1b72 100644
  # --- a/README
  # +++ b/README
  # @@ -4,3 +4,4 @@ new feature
  #  master add new line
  #  merge_conflict_branch
  # +diff me

Changes that have been staged

echo "diff me again" >> README    
git diff --cached    
  #
git add README
git diff --cached
  # diff --git a/README b/README
  # index 4b7c1e3..fbe856c 100644
  # --- a/README
  # +++ b/README
  # @@ -4,3 +4,5 @@ new feature
  #  master add new line
  #  merge_conflict_branch
  # +diff me
  # +diff me again

Unstage a file

echo "to be unstaged" >> README
git add README
git status

  # On branch master
  # Changes to be committed:
  #   (use "git reset HEAD <file>..." to unstage)
  #
  #    modified:   README
  #    

git reset HEAD README

  # Unstaged changes after reset:
  # M    README    

git status

  # # On branch master
  # # Changes not staged for commit:
  # #   (use "git add <file>..." to update what will be committed)
  # #   (use "git checkout -- <file>..." to discard changes in working directory)
  # #
  # #    modified:   README
  # #
  # no changes added to commit (use "git add" and/or "git commit -a")

Restore file to previous version

echo "these changes will be reset" >> README
git status

  # # On branch master
  # # Changes not staged for commit:
  # #   (use "git add <file>..." to update what will be committed)
  # #   (use "git checkout -- <file>..." to discard changes in working directory)
  # #
  # #    modified:   README
  # #
  # no changes added to commit (use "git add" and/or "git commit -a")

git checkout -- README
git status

  # # On branch master
  # nothing to commit, working directory clean

Reset all tracked files to previous commit

git reset --hard

Deletes all changes since last commit
Only affects tracked files
Untracked files do not get deleted

Working with remotes

(e.g. GitHub, your own server, etc)

Push Changes to Remote

Add a remote to you bare repo

“git push repo_name branch_to_push”

git remote -v
  # 
git init ../git.git --bare
git remote add my_repo ../git.git 
git remote -v

  # my_repo  ../git.git (fetch)
  # my_repo  ../git.git (push)

git push my_repo master

  # Counting objects: 24, done.
  # Delta compression using up to 2 threads.
  # Compressing objects: 100% (14/14), done.
  # Writing objects: 100% (24/24), 2.07 KiB | 0 bytes/s, done.
  # Total 24 (delta 1), reused 0 (delta 0)
  # To ../git.git
  #  * [new branch]      master -> master

Clone from a remote repo

  git clone ../git.git ../git_clone
  cd ../git_clone
  git remote -v
     # origin    /Users/user/test_git/../git.git (fetch)
     # origin    /Users/user/test_git/../git.git (push)

“origin” is the default name of your git repo that you have access to

Download changes from a Remote URL

  # git fetch remote_name
  git fetch origin

Does not merge into your existing code, just downloads all changes locally so can merge / checkout

Merge Changes from Remote Branch

  git fetch origin
  git merge origin/master master
    #  **fix any conficts if needed and commit**
    # can also do "git pull origin"

Workflow for pushing to a Repo

Clone from Repo
```
git clone url_to_git_repo
```

Go into directory and make changes

cd url_to_git_repo
echo "cloned" >> README

Commit your changes
```
git commit -am "my changes"
```
Fetch and merge from origin
```
git pull origin
```

Fix conflicts (if any)

git commit -am "merged origin to masteR"

Push to origin
```
git push origin master
```

GitHub Pull Requests

Fork a project
Clone locally
Add remote to project you forked from (typically called “upstream”)
```
git remote add upstream git.repo
```
Make your changes

Make your commit

git pull upstream/master master
*resolve conflicts*
git commit

Use web interface to create pull request
Go to your fork
Sidebar > Pull Request

Note: Markdown was a pain. It rendered the HTML but a mix of tabs and spaces and even manual spacing caused inconsistent behaviour.

Quickstart: Git

Introduction

Configuration

Initialise

See current status and branch

Save (Commit) files into the Repo

Status of Files

Staging Files

Viewing previous commit logs

See previous commit states

Ignoring Files

Branches

View Branches

Create New Branch

Switch to new branch

Merging Branches

Delete Branch after use

Merge Conflicts

Show changes

Unstage a file

Restore file to previous version

Reset all tracked files to previous commit

Working with remotes

Push Changes to Remote

Clone from a remote repo

Download changes from a Remote URL

Merge Changes from Remote Branch

Workflow for pushing to a Repo

GitHub Pull Requests

Published by thewheat

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Introduction

Configuration

Initialise

See current status and branch

Save (Commit) files into the Repo

Status of Files

Staging Files

Viewing previous commit logs

See previous commit states

Ignoring Files

Branches

View Branches

Create New Branch

Switch to new branch

Merging Branches

Delete Branch after use

Merge Conflicts

Show changes

Unstage a file

Restore file to previous version

Reset all tracked files to previous commit

Working with remotes

Push Changes to Remote

Clone from a remote repo

Download changes from a Remote URL

Merge Changes from Remote Branch

Workflow for pushing to a Repo

GitHub Pull Requests

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