Udacity Git & Github Course Notes

2020/01/07 20:14 PM posted in  Udacity Git & Github Course
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Review A Repo's History

git log - display all of the commits of a repository

  • the SHA
  • the author
  • the date
  • the message
  • ...and more

git log --oneline (use flag to alter display)

  • lists one commit per line
  • shows the first 7 characters of the commit's SHA
  • shows the commit's message

git log --stat

  • displays the file(s) that have been modified
  • displays the number of lines that have been added/removed
  • displays a summary line with the total number of modified files and lines that have been added/removed

command line pager

git log -p (flag short for --patch)

  • git log -p -w (-w flag ignores whitespace changes)
  • displays the files that have been modified
  • displays the location of the lines that have been added/removed
  • displays the actual changes that have been made
  • git log -p SHA OR git show -SHA to look into a specific commit

Add Commits to A Repo

git add <file1> <file2>...<fileN>

  • move files from the Working Directory to the Staging Index
  • git add . refers to the all files and directories in current directory

git rm --cached

  • removes file from the Staging Index

git commit -m "Initial commit"

  • Bypass the editor with the -m flag

What to include in a Commit

  • The goal is that each commit has a single focus

What makes good commit messages?

Do

  • do keep the message short (less than 60-ish characters)
  • do explain what the commit does (not how or why!)

Do not

  • do not explain why the changes are made (more on this below)
  • do not explain how the changes are made (that's what git log -p is for!)
  • do not use the word "and"

What if you want to explain the Why


The information in red box is included in the git log.

Udacity Git Commit Message Style Guide

git diff

  • to see changes that have been made but haven't been committed, yet.
    • the files that have been modified
    • the location of the lines that have been added/removed
    • the actual changes that have been made
  • same as git log -p

Having Git Ignore Files

  • add .gitignore file to the same directory that the hidden .git directory is located

What if there are a lot files to ignore?

Tagging, Branching, and Merging

Tagging

  • git tag -a v1.0 (SHA)
    • without providing SHA, git will tag the most recent commit
    • -aflag (always use this flag) tells Git to create an annotated flag which include a lot of extra information such as:
      • the person who made the tag
      • the date the tag was made
      • a message for the tag
  • to delete a tag git tag -d v1.0

Branching

  • git branch (name) (SHA)

    • list all branch names in the repository
    • create new branches
    • delete branches (git branch -d (name))
      • can't delete a branch that you're currently on.
      • can't delete a branch that has unique commit
      • To force deletion, git branch -D sidebar

  • git checkout (name)

    • will remove all of the files that are referenced by commits in the master branch.
    • will replace them with the files that are referenced by the commits in the sidebar branch.
    • HEAD indicator pointing to the branch

  • git checkout -b footer master

    • create a branch and switch to it in one command

  • See all branches at once

    • git log --oneline --graph --all

Merging

  • regular merge & fast-forward merge
  • making a merge makes a commit
  • git merge <other-branch>merge into the current 'checkout' branch

Merge Conflicts

  • a merge conflict occurs when Git isn't sure which line(s) you want to use from the branches that are being merged.
  • so we need to edit the same line on two different branches and then try to merge them.
  • Steps to solve merge conflicts
    • locate and remove all lines with merge conflict indicators
    • determine what to keep
    • save the file(s)
    • stage the file(s)
    • make a commit

Undoing Changes

Changing The Last Commit

git commit --amend

  • If your Working Directory is clean, it will let you provide a new commit message.
  • Add Forgotten Files (or changes to files) To Commit
    • edit the file(s)
    • save the file(s)
    • stage the file(s)
    • and run git commit --amend

Reverting A Commit

git revert

  • git revert <SHA-of-commit-to-revert>
  • will undo the changes that were made by the provided commit
  • creates a new commit to record the change

Relative Commit References

Resetting Commits

git reset <reference-to-commit>

  • move the HEAD and current branch pointer to the referenced commit
  • erase commits
    • flag --hard
  • move committed changes to the staging index
    • flag --soft
  • unstage committed changes
    • flag --mixed (default without flag)
  • before doing any resetting, create backup branch on the most-recent commit git branch backup

Back To Normal

  1. remove the uncommitted changes from the working directory
    • git checkout -- index.html
  2. merge backup into master (which will cause a Fast-forward merge and move master up to the same point as backup)
    • git merge backup

Remote Repositories

Add A Remote Repository

  • git remote add origin <url> to set the shortname
  • git remote -v to see the full path to the remote repository

Push Changes To A Remote

  • git push <remote-shortname> <branch>

Pulling Changes From A Remote

  • git pull <remote-shortname> <branch>

Pull vs Fetch

  • git pull do two things:
    • fetching remote changes (which adds the commits to the local repository and moves the tracking branch to point to them)
    • merging the local branch with the tracking branch
  • below is when we cannot use git pull origin master

Working On Another Developer's Repository

Reviewing Existing Work

Filter Commits By Author

  • git shortlog -s -n

    • -s to show just the number of commits
    • -n to sort them numerically

  • git log --author=surma

Filter Commits By Search

--grepflag

  • git log --grep=bug
  • git log --grep="unit tests"
  • Grep is a pattern matching tool

Determining What To Work On

  • checkCONTRIBUTING.mdfile
  • GitHub Issues

Topic Branches

Update The README

Staying In Sync With A Remote Repository

Create a Pull Request

  • A pull request is a request to the original or source repository's maintainer to include changes in their project that you made in your fork of their project. You are requesting that they pull in changes you've made.

Recap

A pull request is a request for the source repository to pull in your commits and merge them with their project. To create a pull request, a couple of things need to happen:

  • you must fork the source repository
  • clone your fork down to your machine
  • make some commits (ideally on a topic branch!)
  • push the commits back to your fork
  • create a new pull request and choose the branch that has your new commits

Retrieving Upstream Changes

  • git fetch upstream master

Manage an active PR
If the project's maintainer is requesting changes to the pull request, then:

  • make any necessary commits on the same branch in your local repository that your pull request is based on
  • push the branch to the your fork of the source repository

The commits will then show up on the pull request page.

Squash Commits

The Rebase Commandgit rebase -i HEAD~3

  • HEAD~3as the base where all of the other commits (HEAD~2, HEAD~1, HEAD) will connect to. (HEAD point to current location)
  • -i in the command stands for "interactive".