Git courses

Try Git

Via Code School

Init, status

git init to initialize a repo.
git status to see what the current state of the local repo is. - staged: ready to be committed. - unstaged: changed files that have not been prepared to be committed. - untracked: not tracked by Git. - deleted: deleted, waiting to be removed by Git.

Add, reset, log

git add <filepath>: add to Git - git add . to add all files in current directory and under it. - git add '*.txt': add all TXT files. (quotes are important: Git wants to add all files in subdirs too).
git reset <filepath>: remove from staging area.
Staging area: where we group files before we commit them to Git.
Commit: a snapshot of your repo.
git log: details of each commit. - git log --summary: even more details of each commit.

Add remote, push, pull to remote

Typical to call the main remote origin.
git remote add origin git@github.com:asimihsan/try_git.git: add a remote called origin with that URI.
git push -u <remote_name> <branch_name>: Push the local branch to that remote. - -u means remember the parameters - git push -u origin master: push the local master branch to the origin remote, whilst remembering the parameters.
See Customizing Git - Git Hooks for how to do cool things every time you push, e.g. upload to webserver.
git pull <remote_name> <branch_name>: pull the remote into the local branch.
Sometimes when you want to pull you have changes you don't want to commit. - git stash will stash your changes. - git stash apply to re-apply the changes after the pull.

Differences

HEAD is a pointer to the most recent commit.
git diff <pointer>: pointer is either SHA digest or some alias, e.g. HEAD.
Try to commit different files in unique commits.
git diff --staged: changes in your staged files (e.g. add-ed).

Undo

git checkout -- <target>: change files to how they were at the last commit for the target. - Using -- because we're promising the command-line that there aren't any more parameters. Allows us to have a branch called <target>.

Branching

git branch <branch_name>: create a local branch.
git checkout <branch_name>: switch to a branch.
git checkout -b <branch_name>: both create and switch to a new branch.
git branch: see all local branches.

Removing

git rm '-*.txt': remove all TXT files.
git rm -r folder: recursively remove all folders and files from folder.
If you accidentally delete a file before git rm it, you can do git commit -a to auto-remove deleted files with a commit.

### Merging, deleting branches

git checkout <branch_name>
Do stuff
git checkout master
git merge <branch_name>: merge another branch into the current branch.
git branch -d <branch_name>: delete branch - By default can't delete a branch that hasn't been merged (there's a risk you're being a muppet!) - git branch -d --force <branch_name> to force delete an unmerged branch. - git branch -D <branch_name> for shortcut to force delete unmerged branch.

Git Real

Via Code School

Level 1: Introduction

Distributed: everyone has a copy of the repo, not centralised.
Initial config:

git config --global user.name "Asim Ihsan" git config --global user.email user@host.com git config --global color.ui true
Git workflow - Create a file. - Add file to staging area - Commit changes. - Modify file again. - Add file to staging area. - Commit changes. - etc.

Level 2: Staging and Remotes

To find unstaged differences since last commit, git diff.
Once you git add (stage) then git diff it won't show anything! - git diff --staged to diff the staged files.
git reset HEAD <file> to unstage files.
HEAD is the last commit on the current branch / timeline that we're on.
git checkout -- <filename> to restore file to state at last commit.
git commit -a -m "message" to add changes from all tracked files; untracked files are ignored.

How to undo

Only do these command before you push.
git reset --soft HEAD^ to undo last commit, put changes into staging. You will move to the previous commit.
git commit --amend -m "modify" to add our stage to the previous commit, and overwrite the previous commit message with a new one.
git reset --hard HEAD^: undo last commit and all changes will be lost. You will move to the previous commit.
git reset --hard HEAD^^ undo the last two commits and all changes will be lost. You will move two commits back.

How to share

git doesn't do access control. If you need this use a hosted or self-managed solution.
Hosted: - GitHub - BitBucket
Self-Managed - Gitosis - Gitorious - GitLab
git remote add origin <url>: add a remote called "origin" with a URL.
git remote -v: show remote repositories
git push -u origin master: push local branch called "master" to remote called "origin". - You'll need to use password caching if you don't want to type in password every time. - -u stores this remote and branch as default.
git pull: pull changes down from the remote
Common to have multiple remotes - origin - test - production
git remote rm <name> to remove remote

Level 3: Cloning and Branching

Collaborating

Find e.g. GitHub URL, then git clone <URL>.
Or change name of clone directory, git clone <URL> <name>.

Branches

git branch <branch_name>: create a branch name, but don't switch to it.
git checkout <branch_name>: switch timelines to another branch.
Once you're done with a feature branch you want to merge it into the main master branch.
git checkout master.
git merge <branch_name>: merge another branch called "branch_name" into the current branch (master).
On merging it says it is "fast-forwarding". What does that mean? - We've made changes to the feature branch without any interim changes on the master branch. - It is very easy to merge: just "fast-forward".
Once you're done with a branch then delete it.
git branch -d <branch_name>: delete a branch.
git checkout -b <branch_name>: create then switch to a branch.
Complex merges can't use fast-forward, and git creates a new commit with a message.

Level 4: Collaboration Basics

git add --all to add all tracked files to the stage.
Suppose you're working on a file locally, and someone pushes changes to it that you haven't pulled.
If you git push now, you'll get "rejected".
You could git pull then git push, and it'll work.
But what does git pull do? - Fetch (or sync) our local repo with the remote one. This is the same as git fetch. - But this doesn't update any local code! It actually fetches to origin/master. - The second step is it merges origin/master with master. This is the same as git merge origin/master.
Hence git pull is actually: 1. git fetch. 2. git merge origin/master.
Some people think "merge commits" via git pull pollutes the log. - rebase is one way to get around this.

Merge conflict

Suppose git pull hits a merge conflict?
git status will emphasise this.
Editing the file will reveal the commit, and then you'll manually need to fix it. - First section are your changes, second section are their changes. - Handily, these sections are labelled "HEAD" or "".
After resolving a conflict just git commit -a without a commit message because git will auto-fill a useful message mentioning the conflict for you.

Level 5: Remote Branches and Tags

When you need other people to work on your branch.
Any branch that will last more than a day.
git checkout -b <branch_name>.
git push <remote_name> <branch_name>: push branch to remote. - Don't need a -u; subsequent push will know that this is the current tracking branch.
A subsequent git pull will tell people about the new remote branch.
However, a git branch (list all local branches) won't reveal it.
git branch -r to list all remote branches.
git remote show origin: show all remotes, and whether their branches are tracked or not, and status of local branches wrt remote branches.
git push <remote_name> :<branch_name>: delete remote branch.
git branch -d <branch_name>: delete local branch. - If any unmerged changes in branch git will default to preventing this.
git branch -D <branch_name>: delete local branch, ignoring unmerged changes.
What happens if you push and the remote branch doesn't exist any more? - No easy error messages. - You want to git remote show <remote name> - git will say "stale" to indicate a local branch that no longer has corresponding remote branch.
git remote prune <remote_name>: clean up deleted remote branches.

Heroku

Heroku only deploys off of the master branch.
Hence if you push to some other branch, e.g. git push heroku-staging staging, it won't deploy.
git push heroku-staging staging:master will push to remote called 'heroku-staging' with local:remote branches. - Push from staging to master.

Level 6: Rebase Belong to Us

Merge commits are bad, pollute the log.
Instead of git pull then git push, we're going to do: - git fetch (the first step of git pull, no merging). - git rebase.
What does git rebase do? 1. Move all changes to master which are not in origin/master to a temporary area. 2. Run all origin/master commits onto master, one at a time. 3. Run all commits in the temporary area onto master, one at a time.

Work flow (before)

Work on branch.
git checkout master
git merge <branch_name>.

Work flow (rebase)

Work on branch.
git rebase master: run the master commits one at a time on the branch.
git checkout master
git merge <branch_name>: this will do a fast-forward.

Conflicts

git fetch to update our knowledge of the remote.
git rebase
But now we hit a conflict! You have options, because remember rebase runs commits one at a time. 1. Fix the conflict indicated, do a git add <filename>, then run git rebase --continue to continue the rebase. 2. Skip this patch, git rebase --skip. 3. Abort the rebasing, git rebase --abort.
During a rebase you will not be in a branch, so expect this during a git status.

#### Rebase vs merge

If the branch has been around for a long time, probably want a merge to track when you merged it with a log of what got changed.
If it's a short-lived feature rebase avoids the pollution of the logs.

Level 7: History and Configuration

git log to view previous commits. - SHA hash, author, date, message.
git config --global color.ui true to colourise the output.
git log --pretty=oneline for line-based log with <hash> <commit message> per line.
git log --pretty=format:"%h %ad- %s [%an]" for a customizable format for log.
git log --oneline -p will show patch-output for commits; what lines added/removed/modified.
git log --oneline --stat will show counts of lines added/removed/modified for each commit.
git log --oneline --graph for graph visualisation of the timelines.

Date Ranges

git log --until=1.minute.ago for until.
git log --since=1.day.ago for since in days.
git log --since=1.hour.ago for since in hours.
git log --since=1.month.ago --until=2.weeks.ago for since and until (relative).
git log --since=2000-01-01 --until=2012-12-21 for since and until (absolute).

Diff

git diff for patch diff since last commit.
git diff HEAD is the same as git diff.
git diff HEAD^^ goes two commits ago
git diff HEAD~5 goes five commits ago.
git diff HEAD^..HEAD compares second most recent commit vs. most recent commit.

Earlier commits

git diff <SHA1>..<SHA2> to compare between range of SHAs. - Can also use abbreviated SHAs, last 7 hex digits.
git diff master bird: diff branches
git diff --since=1.week.ago --until=1.minute.ago: time-based diff.

Blame

git blame <filename> --date short: figure out what commits, with date and author, changed what lines.

Excluding from local copy

Want to exclude from local repo, not from remote or from other people's locals.
Put patterns into .git/info/exclude.

Excluding from all copies

Use .gitignore to exclude patterns from all local repos and remote repo.

Removing files

git rm <filename> to remove.
Then git commit.

Untracking files

Sometimes don't want to delete, just want to tell git "stop tracking this file".
git rm --cached <filename> to stop tracking a file.
Afterwards git status will say it's been deleted but it won't be deleted from your file system, only from Git.

Config

git config --global user.name "My name"
git config --global user.email "user@host.com"
git config --global core.editor emacs to change editor
git config --global merge.tool opendiff to use a different diff tool.
Without the --global flag you can configure per-repo variables.
git config --list to see current config.

Aliases

git config --global alias.mylog "log --pretty=format:'%h %s [%an]' --graph" to create a log alias
git config --global alias.lol "log --graph --decorate --pretty=oneline --abbrev-commit --all" for a popular log output format.
To use then call git mylog or git lol.
Alias your frequent commands.

Other commands I've found

git revert HEAD: revert changes introduced by a particular commit, add new commit to track this. Used when you want to revert pushed changes.

References

git-scm homepage - full book for free as well.
github help page
git immersion - overview of git.
git ready - Good reference.
git from the bottom up - PDF of the technical internals of git.
git internals PDF - More git internals
git-flow blog post - Philosophy to git branching and merging and pushing.

Files

[course] git.md

Latest commit

History

[course] git.md

File metadata and controls

Git courses

Try Git

Init, status

Add, reset, log

Add remote, push, pull to remote

Differences

Undo

Branching

Removing

Git Real

Level 1: Introduction

Level 2: Staging and Remotes

How to undo

How to share

Level 3: Cloning and Branching

Collaborating

Branches

Level 4: Collaboration Basics

Merge conflict

Level 5: Remote Branches and Tags

Heroku

Tags

Level 6: Rebase Belong to Us

Work flow (before)

Work flow (rebase)

Conflicts

Level 7: History and Configuration

Date Ranges

Diff

Earlier commits

Blame

Excluding from local copy

Excluding from all copies

Removing files

Untracking files

Config

Aliases

Other commands I've found

References