====== Git ======

**General Information**

Useful git commands when managing git repos.

Official site: https://git-scm.com/

**Checklist**
  * Distro(s): Enterprise Linux
  * Other: Git repo setup with commit access

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====== Install ======

Git can be installed from repos (older, stable versions) or from source (newest available).

===== Repos =====

Git is available via CentOS default repos
<code bash>
yum install git
</code>

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==== IUS Repos ====

[[https://ius.io/|IUS (Inline with Upstream Stable)]] is a Rackspace sponsored community project to build more recent versions of RPMs for Enterprise Linux.

It is similar to Software Collections, but is a bit easier to use since there is not an environment to "enable".

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Add the IUS Repo
  * CentOS 7<code bash>yum install https://centos7.iuscommunity.org/ius-release.rpm</code>
  * CentOS 6<code bash>yum install https://centos6.iuscommunity.org/ius-release.rpm</code>

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Remove the system provided version (if installed)<code bash>yum remove git</code>

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Install the IUS git version<code bash>yum install git2u</code>

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Verify version<code bash>git --version</code>

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====== Initial Git Config Setup ======

Setup your user name for commits:
<code bash>
git config --global user.name "USERNAME"
</code>
\\

E-mail config can be setup with your real e-mail or by keeping your e-mail private:

Option 1: Setup Git e-mail config - real e-mail
<code bash>
git config --global user.email "YOUR-EMAIL@DOMAIN.com"
</code>

Option 2: Setup Git e-mail config - keep e-mail hidden
<code bash>
git config --global user.email "USERNAME@users.noreply.github.com"
</code>

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HTTPS Authentication setup - turn on credential cache
<code bash>
git config --global credential.helper cache
</code>

HTTPS Authentication setup - increase auth timeout to 1 hour (3600 seconds)
<code bash>
git config --global credential.helper 'cache --timeout=3600'
</code>

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Disable https verify for self signed certs on a single cloned repo<code bash>git config http.sslVerify false</code>

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Alternatively, configure git to trust self signed certs: https://stackoverflow.com/questions/9072376/configure-git-to-accept-a-particular-self-signed-server-certificate-for-a-partic

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====== Create/Clone Repos ======

Create a new local project (to be pushed up to a repo later)<code bash>git init <project-name></code>

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Download an existing project via URL<code bash>git clone URL</code>

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Download an existing project via HTTPS URL and do not verify ssl cert for self signed<code bash>git -c http.sslVerify=false clone https://URL</code>

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====== File Status ======

List all new or modified files to be committed
<code bash>
git status
</code>

File States
  * **Untracked** => A **new local file has been created** and not yet added to the tracked index list
    * Proceed (add file to be tracked)<code bash>git add <filename></code>
    * Undo (get rid of untracked file):<code bash>rm <filename></code>

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  * **Unstaged changes** => You made **changes to an existing tracked file**, but have not added the current snapshot of the file to the index yet
    * Proceed (add file to staging index)<code bash>git add <filename></code>
    * Undo (undo unstaged local changes)<code bash>git checkout <filename></code>

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  * **Uncomitted changes** => You made changes to a file, and used git add to stage the change in the index, but **need to commit the change to your local copy of a repo**
    * Proceed (local commit changes)<code bash>git commit <filename></code>
    * Undo (undo staged changes)<code bash>git reset <filename></code>

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  * **Committed changes (clean working directory)** => files are committed to the local repo and just **need to be pushed to the remote repo**
    * Proceed (push local committed changes to repo)<code bash>git push</code>
    * Undo (undo local commits)
      * Undo local commits, but preserve file contents<code bash>git reset <last good SHA></code>
      * Undo local commits AND undo file content changes<code bash>git reset --hard <last good SHA></code>

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  * **Pushed changes** => You pushed changes to the repo
    * Proceed: N/A
    * Undo (Undo the last pushed change)
      * View recent commits with diff details<code bash>git log -p</code>
      * Retrieve the commit SHA hash from the above and revert that push<code bash>git revert <SHA></code>

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====== Exclude Files from Tracking ======

A plain text file called '.gitignore' in the project root excludes files and directories from tracking by git.

Full documentation here: https://git-scm.com/docs/gitignore

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Example .gitignore<code bash># Git ignore file - comments are allowed
__pycache__/
*.log
tmp/</code>
  * Do not track any files that
    * Are inside a __pycache__ directory
    * End in .log
    * Are inside a tmp directory

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List all ignored files in the current project<code bash>git ls-files --other --ignored --exclude-standard</code>

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====== Pull, Change, Push ======

The general workflow of making file changes to a git repo:

**Pull**: Update local repo to include remote repo's latest changes
<code bash>
git pull
</code>

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**=> Create new file or make existing file changes <=**

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**Stage**: Snapshots file in preparation for versioning (stages files)
<code bash>
git add [file]
</code>

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**Verify**: Show file differences between staged and the last file version
<code bash>
git diff --staged
</code>

**Undo**: Unstage file, but preserve contents
<code bash>
git reset [file]
</code>

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**Commit Local**: Commit file snapshot to the local repo. (Either newly added file or to an existing file that was changed)
<code bash>
git commit [file] -m "Commit comment here."
</code>

\\

**Commit Remote**: Push your commits to the remote repo.
<code bash>
git push
</code>

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====== Undo Changes ======

**Start Over**: You cloned a repo, made local changes that broke things. To revert back to the initially checked out version:
<code bash>
git checkout .
git pull
</code>

\\
**Undo Git Add**: To revert from "git add" changes (unstage a file)
<code bash>
git reset
</code>

\\
**Undo Git Commit**: To revert from locally committed changes (git commit)
<code bash>
git revert
</code>

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====== Logs and Diffs ======

You can see file differences and logging of changes at different stages in the process.

===== Logs =====

Summary of recent commits (by 'git commit <filename>')
<code bash>
git log
</code>

Details of most recent commits on a single file
<code bash>
git log -p <filename>
</code>

Details of a specific commit #
<code bash>
git log -p <commit#>
</code>

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===== Diffs =====

Summary of changes that will be pushed (with next 'git push')
<code bash>
git diff --stat --cached origin/master
</code>

Details of changes that will be pushed (with next 'git push')
<code bash>
git diff --cached origin/master
</code>

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====== Branches ======

View current branch
<code bash>
git branch
</code>

View all existing branches
<code bash>
git branch -a
</code>

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Create a new branch called "testing"
<code bash>
git checkout -b testing
</code>

Switch between 'master' and 'testing' branches
<code bash>
git checkout master
git checkout testing
</code>

\\

Merge changes from 'testing' branch into the 'master' branch and push changes to the 'master' repo
<code bash>
git checkout master
git merge testing --no-ff
git push
</code>
  * --no-ff => retain all of the commit messages before the merge

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===== Deleting Branches =====

Delete a remote branch<code bash>git push origin --delete <branch-name></code>

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Delete a local branch<code bash>git branch --delete <branch-name></code>

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Prune remote list if remote branches were deleted by someone else<code bash>git remote prune origin</code>

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===== Upstream Repo Sync =====

If your cloned repo is a fork, you will want to keep it synced with the upstream project from time to time.

==== Add Upstream Source ====

Adding the upstream repo to your local cloned fork only needs to be done one time.

  * In the terminal, navigate to the directory of the cloned repo.

  * View current remote repos for the fork:<code bash>git remote -v</code>

  * Add the upstream project<code bash>git remote add upstream https://github.com/UPSTREAM-USERNAME/APPLICATION-NAME.git</code>

  * Verify upstream was added<code bash>git remote -v</code>

==== Syncing Fork to Upstream ====

  * Fetch upstream's commits<code bash>git fetch upstream</code>

  * Check out the local master branch for your fork<code bash>git checkout master</code>

  * Merge changes from the upstream project into the local master branch<code bash>git merge upstream/master</code>

  * Push local changes to your fork on github<code bash>git push origin master</code>

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====== Troubleshooting ======

Fixing different git issues.

===== Extra Characters in git diff =====

* Fix/remove 'ESC[xxx' characters in git diff<code bash>git config --global core.pager "less -R"</code>
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* Fix/remove '^M' characters in git diff<code bash>git config --global core.pager "tr -d '\r' | less -REX"</code>

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