Git

Git Basics

Posted by Lynn on October 5, 2020

Terminology

  • Working Directory

  • Staging Area / Staging Index / Index

    Area

Basic Commands

Create or Clone a Repository

  • Check the repository’s status
    • git status
  • Initial a local repository
    • git init NAME
  • Clone a remote repository to local (default branch: master, default remote name: origin)
    • git clone URL

Review a Repository’s History

  • List all commits
    • git log
      • --oneline
      • --graph
      • --all
      • -p or --patch
      • --stat
  • List specific commit
    • git show SHA

Add Commits to a Repository

  • Add
    • Add files to staging area
      • git add FILE1 FILE2
    • Add all changed files to staging area
      • git add .
  • Commit
    • Record changes in staging area to the repository
      • git commit
    • Use the given message as the commit message
      • git commit -m MESSAGE
  • Diff
    • git diff
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Working Directory      <------+-------+-------+
        |                     |       |       |
        |                     |       |       |
        V                     |       |       |
    "git add"                 |       |     diff
        |                     |       |       |
        |                     |       |       |
        V                     |       |       |
      Index      <----+-------|-------|-------+
        |             |   diff HEAD   |
        |             |       |       |
        V             |       |       |
  "git commit"  diff --cached |   diff HEAD^
        |             |       |       |
        |             |       |       |
        V             |       |       |
      HEAD       <----+-------+       |
        |                             |
        |                             |
        V                             |
previous "git commit"                 |
        |                             |
        |                             |
        V                             |
      HEAD^            <--------------+

Good Commit Messages

  • Explain what the commit does in the first line
  • Explain why in the body
  • No how

Tag, Branch and Merge

  • Tag
    • Create tag
      • git tag TAG
    • Create tag with annotation
      • git tag -a TAG or git tag --annotate TAG
    • Delete tag
      • git tag -d TAG
  • Branch
    • Create branch
      • git branch BRANCH
    • Delete branch
      • git branch -d BRANCH
    • Switch branch or restore working tree files
      • git checkout BRANCH/TAG/SHA
    • Create a branch and switch to it
      • git checkout -b BRANCH
  • Merge
    • git merge BRANCH/TAG/SHA

Undoing Changes

  • Relative Commit References
    • ^ indicates the parent commit
    • ~ indicates the first parent commit
  • Replace the tip of the current branch by creating a new commit
    • git commit --amend
  • Revert an existing commit
    • git revert SHA
  • Reset current HEAD to the specified state
    • git reset SHA
      • --mixed
      • --soft
      • ---hard
      • Video

Git Collaboration

Working With Remotes

Remote Repository

  • Remote
    • git remote
      • -v
      • add REMOTE URL
      • rename OLD NEW
      • remove REMOTE
  • Update remote refs along with associated objects
    • git push
  • Download objects and refs from another repository
    • git fetch
  • Fetch from and integrate with another repository or a local branch
    • git pull = git fetch + git merge

Working On Another Developer’s Repository

  • Fork repository
  • Summarize ‘git log’ output
    • git shortlog
      • -s
      • -n
      • --author=NAME
      • --grep=REGEX

Staying In Sync With A Remote Repository

  • Pull request
  • Stay in sync with source project
    • origin
    • upstream
  • Reapply commits on top of another base tip
    • git rebase -i BASE

References

GitHub & Collaboration

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