--- category: tool tool: git contributors: - ["Jake Prather", "http:#github.com/JakeHP"] filename: LearnGit.txt --- Git is a distributed version control and source code management system. It does this through a series of snapshots of your project, and it works with those snapshots to provide you with functionality to version and manage your source code. ## Versioning Concepts ### What is version control? Version control is a system that records changes to a file, or set of files, over time. ### Centralized Versioning VS Distributed Versioning * Centralized version control focuses on synchronizing, tracking, and backing up files. * Distributed version control focuses on sharing changes. Every change has a unique id. * Distributed systems have no defined structure. You could easily have a SVN style, centralized system, with git. [Additional Information](http://git-scm.com/book/en/Getting-Started-About-Version-Control) ### Why Use Git? * Can work offline. * Collaborating with others is easy! * Branching is easy! * Merging is easy! * Git is fast. * Git is flexible. ## Git Architecture ### Repository A set of files, directories, historical records, commits, and heads. Imagine it as a source code datastructure, with the attribute that each source code "element" gives you access to its revision history, among other things. A git repository is comprised of the .git directory & working tree. ### .git Directory (component of repository) The .git directory contains all the configurations, logs, branches, HEAD, and more. [Detailed List.](http://gitready.com/advanced/2009/03/23/whats-inside-your-git-directory.html) ### Working Tree (component of repository) This is basically the directories and files in your repository. It is often referred to as your working directory. ### Index (component of .git dir) The Index is the staging area in git. It's basically a layer that separates your working tree from the Git repository. This gives developers more power over what gets sent to the Git repository. ### Commit A git commit is a snapshot of a set of changes, or manipulations to your Working Tree. For example, if you added 5 files, and removed 2 others, these changes will be contained in a commit (or snapshot). This commit can then be pushed to other repositories, or not! ### Branch A branch is essentially a pointer that points to the last commit you made. As you commit, this pointer will automatically update and point to the latest commit. ### HEAD and head (component of .git dir) HEAD is a pointer that points to the current branch. A repository only has 1 *active* HEAD. head is a pointer that points to any commit. A repository can have any number of heads. ### Conceptual Resources * [Git For Computer Scientists](http://eagain.net/articles/git-for-computer-scientists/) * [Git For Designers](http://hoth.entp.com/output/git_for_designers.html) ## Commands ### init Create an empty Git repository. The Git repository's settings, stored information, and more is stored in a directory (a folder) named ".git". ```bash $ git init ``` ### config To configure settings. Whether it be for the repository, the system itself, or global configurations. ```bash # Print & Set Some Basic Config Variables (Global) $ git config --global user.email $ git config --global user.name $ git config --global user.email "MyEmail@Zoho.com" $ git config --global user.name "My Name" ``` [Learn More About git config.](http://git-scm.com/docs/git-config) ### help To give you quick access to an extremely detailed guide of each command. Or to just give you a quick reminder of some semantics. ```bash # Quickly check available commands $ git help # Check all available commands $ git help -a # Command specific help - user manual # git help $ git help add $ git help commit $ git help init ``` ### status To show differences between the index file (basically your working copy/repo) and the current HEAD commit. ```bash # Will display the branch, untracked files, changes and other differences $ git status # To learn other "tid bits" about git status $ git help status ``` ### add To add files to the current working tree/directory/repo. If you do not `git add` new files to the working tree/directory, they will not be included in commits! ```bash # add a file in your current working directory $ git add HelloWorld.java # add a file in a nested dir $ git add /path/to/file/HelloWorld.c # Regular Expression support! $ git add ./*.java ``` ### branch Manage your branches. You can view, edit, create, delete branches using this command. ```bash # list existing branches & remotes $ git branch -a # create a new branch $ git branch myNewBranch # delete a branch $ git branch -d myBranch # rename a branch # git branch -m $ git branch -m myBranchName myNewBranchName # edit a branch's description $ git branch myBranchName --edit-description ``` ### checkout Updates all files in the working tree to match the version in the index, or specified tree. ```bash # Checkout a repo - defaults to master branch $ git checkout # Checkout a specified branch $ git checkout branchName # Create a new branch & switch to it, like: "git branch ; git checkout " $ git checkout -b newBranch ``` ### clone Clones, or copies, an existing repository into a new directory. It also adds remote-tracking branches for each branch in the cloned repo, which allows you to push to a remote branch. ```bash # Clone learnxinyminutes-docs $ git clone https://github.com/adambard/learnxinyminutes-docs.git ``` ### commit Stores the current contents of the index in a new "commit." This commit contains the changes made and a message created by the user. ```bash # commit with a message $ git commit -m "Added multiplyNumbers() function to HelloWorld.c" ``` ### diff Shows differences between a file in the working directory, index and commits. ```bash # Show difference between your working dir and the index $ git diff # Show differences between the index and the most recent commit. $ git diff --cached # Show differences between your working dir and the most recent commit $ git diff HEAD ``` ### grep Allows you to quickly search a repository. Optional Configurations: ```bash # Thanks to Travis Jeffery for these # Set line numbers to be shown in grep search results $ git config --global grep.lineNumber true # Make search results more readable, including grouping $ git config --global alias.g "grep --break --heading --line-number" ``` ```bash # Search for "variableName" in all java files $ git grep 'variableName' -- '*.java' # Search for a line that contains "arrayListName" and, "add" or "remove" $ git grep -e 'arrayListName' --and \( -e add -e remove \) ``` Google is your friend; for more examples [Git Grep Ninja](http://travisjeffery.com/b/2012/02/search-a-git-repo-like-a-ninja) ### log Display commits to the repository. ```bash # Show all commits $ git log # Show X number of commits $ git log -n 10 # Show merge commits only $ git log --merges ``` ### merge "Merge" in changes from external commits into the current branch. ```bash # Merge the specified branch into the current. $ git merge branchName # Always generate a merge commit when merging $ git merge --no-ff branchName ``` ### mv Rename or move a file ```bash # Renaming a file $ git mv HelloWorld.c HelloNewWorld.c # Moving a file $ git mv HelloWorld.c ./new/path/HelloWorld.c # Force rename or move # "existingFile" already exists in the directory, will be overwritten $ git mv -f myFile existingFile ``` ### pull Pulls from a repository and merges it with another branch. ```bash # Update your local repo, by merging in new changes # from the remote "origin" and "master" branch. # git pull $ git pull origin master ``` ### push Push and merge changes from a branch to a remote & branch. ```bash # Push and merge changes from a local repo to a # remote named "origin" and "master" branch. # git push # git push => implicitly defaults to => git push origin master $ git push origin master ``` ### rebase (caution) Take all changes that were committed on one branch, and replay them onto another branch. *Do not rebase commits that you have pushed to a public repo*. ```bash # Rebase experimentBranch onto master # git rebase $ git rebase master experimentBranch ``` [Additional Reading.](http://git-scm.com/book/en/Git-Branching-Rebasing) ### reset (caution) Reset the current HEAD to the specified state. This allows you to undo merges, pulls, commits, adds, and more. It's a great command but also dangerous if you don't know what you are doing. ```bash # Reset the staging area, to match the latest commit (leaves dir unchanged) $ git reset # Reset the staging area, to match the latest commit, and overwrite working dir $ git reset --hard # Moves the current branch tip to the specified commit (leaves dir unchanged) # all changes still exist in the directory. $ git reset 31f2bb1 # Moves the current branch tip backward to the specified commit # and makes the working dir match (deletes uncommited changes and all commits # after the specified commit). $ git reset --hard 31f2bb1 ``` ### rm The opposite of git add, git rm removes files from the current working tree. ```bash # remove HelloWorld.c $ git rm HelloWorld.c # Remove a file from a nested dir $ git rm /pather/to/the/file/HelloWorld.c ``` ## Further Information * [tryGit - A fun interactive way to learn Git.](http://try.github.io/levels/1/challenges/1) * [git-scm - Video Tutorials](http://git-scm.com/videos) * [git-scm - Documentation](http://git-scm.com/docs) * [Atlassian Git - Tutorials & Workflows](https://www.atlassian.com/git/) * [SalesForce Cheat Sheet](https://na1.salesforce.com/help/doc/en/salesforce_git_developer_cheatsheet.pdf) * [GitGuys](http://www.gitguys.com/)