Difference between revisions of "DPS909 & OSD600 Winter 2017"

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(Week 4)
(Week 4)
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** Relationship of <code>git commit</code> with branches
 
** Relationship of <code>git commit</code> with branches
 
*** commit SHA: <code>e0ee2b5acd01acbe5b0bc1ee24b73e5d53a1fd70</code> or shortened to <code>e0ee2b5</code>
 
*** commit SHA: <code>e0ee2b5acd01acbe5b0bc1ee24b73e5d53a1fd70</code> or shortened to <code>e0ee2b5</code>
*** <code>HEAD</code>: the most recent commit
+
*** <code>HEAD</code>: the most recent commit (NOTE: you can also do <code>HEAD~2</code> to mean 2 commits older than <code>HEAD</code> or <code>HEAD~5</code> to mean 5 commits older than <code>HEAD</code>),
 
*** branch: an easy to remember name we give to the current commit, e.g., <code>master</code>
 
*** branch: an easy to remember name we give to the current commit, e.g., <code>master</code>
 
*** <code>master</code> branch vs. "Topic Branches": '''all work happens on a new branch'''
 
*** <code>master</code> branch vs. "Topic Branches": '''all work happens on a new branch'''
 
** creating, switching between, updating
 
** creating, switching between, updating
 
*** <code>git branch <branch name></code>: <code>-d</code> (maybe delete), <code>-D</code> (force delete), <code>-m</code> (rename), <code>-a</code> (list all)
 
*** <code>git branch <branch name></code>: <code>-d</code> (maybe delete), <code>-D</code> (force delete), <code>-m</code> (rename), <code>-a</code> (list all)
*** <code>git checkout <branch name | commit SHA></code>, discussion of "detated HEAD"
+
*** <code>git checkout <branch name | commit SHA></code>, discussion of "detached HEAD"
 
*** <code>git checkout -b <branch name> [<base commit> | HEAD]</code>(create if doesn't exist, checkout new branch)
 
*** <code>git checkout -b <branch name> [<base commit> | HEAD]</code>(create if doesn't exist, checkout new branch)
 
*** <code>git checkout -B <branch name> [<base commit> | HEAD]</code> (create or reset, checkout new branch)
 
*** <code>git checkout -B <branch name> [<base commit> | HEAD]</code> (create or reset, checkout new branch)
 
** local vs. remote, tracking branches
 
** local vs. remote, tracking branches
 +
*** Branches are '''always local''' to your current repo
 +
*** <code>git branch -a</code> will show all of your branches, and any/all '''remote branches''' (i.e., branches in remote repos your repo knows about via <code>git fetch</code>)
 +
*** Example: <code>git checkout -b bug123 friend-repo/bug123</code> will create a branch '''bug123''' locally that is pointing at the same commit as the remote repo '''friend-repo''''s '''bug123''' branch.
 +
*** Any branch you check out that is based on a remote branch will be '''tracked''' by git, and any commits they have ahead of you, or you have ahead of them, will get reported
 
** common workflow
 
** common workflow
 
*** <code>git checkout master</code> - switch to master branch
 
*** <code>git checkout master</code> - switch to master branch
Line 94: Line 98:
 
**** fast-forward merge - given identical histories, move the branch ahead in the history to the new tip
 
**** fast-forward merge - given identical histories, move the branch ahead in the history to the new tip
 
**** 3-way merge - divergent histories, use common ancestor commit (commit 1), and two branch tops (2, 3)
 
**** 3-way merge - divergent histories, use common ancestor commit (commit 1), and two branch tops (2, 3)
 
 
*** recall that <code>git pull</code> does a <code>git fetch</code> and <code>git merge</code> in one step
 
*** recall that <code>git pull</code> does a <code>git fetch</code> and <code>git merge</code> in one step
 
** rebasing
 
** rebasing
 +
*** Replay a series of commits on a different branch vs. the current one, rewriting its history
 +
*** Often done with '''squashing''' (combining multiple commits into a single commit) on topic branches before merging with <code>master</code> to simplify the history
 +
*** Because it rewrites history, you shouldn't do it on branches shared with other developers
 +
*** <code>git rebase <new-base></code>
 +
*** After a rebase, it's easy to do '''fast-forward''' merges
 +
*** <code>git rebase -i</code> starts an interactive rebase, and lets you specify what to do with each commit.  <code>git rebase --abort</code> let's you stop it mid-way through.
 +
*** If you need to squash the last few commits, you can use <code>git rebase -i HEAD~2</code> for example.
 
** gh-pages
 
** gh-pages
  

Revision as of 16:31, 30 January 2017

Resources for DPS909 & OSD600

Week 1

  • Course introduction
  • Some questions:
    • What was the first video game you ever played?
    • What are your main technical strengths, which technologies do you know well and enjoy?
    • Which (new) technologies are you excited to learn and try?
    • When you hear "open source," what comes to mind?
    • Do you have any hesitation, fears, or anxieties about working in open source projects?
  • How to have Success in this course:
    • Willingness to be lost and not panic
    • Willingness to put yourself out there, jump in
    • Curiosity
    • Being driven, persistence
    • Willingness to ask for help
    • Willingness to give others help
    • Independent learning
    • Doing more than the bare minimum

Week 2

Week 3

Week 4

  • Working with git Branches
    • Lightweight, movable, reference (or pointer) to a commit
    • Series of commits: a branch is the furthest tip of a line of commits
    • It is always safe to branch, it won't change the code in any way
    • Relationship of git commit with branches
      • commit SHA: e0ee2b5acd01acbe5b0bc1ee24b73e5d53a1fd70 or shortened to e0ee2b5
      • HEAD: the most recent commit (NOTE: you can also do HEAD~2 to mean 2 commits older than HEAD or HEAD~5 to mean 5 commits older than HEAD),
      • branch: an easy to remember name we give to the current commit, e.g., master
      • master branch vs. "Topic Branches": all work happens on a new branch
    • creating, switching between, updating
      • git branch <branch name>: -d (maybe delete), -D (force delete), -m (rename), -a (list all)
      • git checkout <branch name | commit SHA>, discussion of "detached HEAD"
      • git checkout -b <branch name> [<base commit> | HEAD](create if doesn't exist, checkout new branch)
      • git checkout -B <branch name> [<base commit> | HEAD] (create or reset, checkout new branch)
    • local vs. remote, tracking branches
      • Branches are always local to your current repo
      • git branch -a will show all of your branches, and any/all remote branches (i.e., branches in remote repos your repo knows about via git fetch)
      • Example: git checkout -b bug123 friend-repo/bug123 will create a branch bug123 locally that is pointing at the same commit as the remote repo friend-repo's bug123 branch.
      • Any branch you check out that is based on a remote branch will be tracked by git, and any commits they have ahead of you, or you have ahead of them, will get reported
    • common workflow
      • git checkout master - switch to master branch
      • git pull upstream master - pull in any new commits from the upstream/master branch
      • git checkout -b issue-1234 - create a topic branch for your work, named with bug #
      • git add files - edit files, add to staging area
      • git commit -m "Fix #1234: ..." - commit changes, referencing bug # in commit message
      • git push origin issue-1234 - push your topic branch (and all commits) to your origin repo
      • create pull request
    • merging
      • A merge in git is a way of combining branches into a single branch/history
      • We always fix bugs and add features on new branches, but then we need to merge them back into the main master branch
      • Merging doesn't change any of the branches it combines, it simply connects them.
      • git merge <branch name> merges <branch name> into the currently checked out branch
      • Different merge algorithms
        • fast-forward merge - given identical histories, move the branch ahead in the history to the new tip
        • 3-way merge - divergent histories, use common ancestor commit (commit 1), and two branch tops (2, 3)
      • recall that git pull does a git fetch and git merge in one step
    • rebasing
      • Replay a series of commits on a different branch vs. the current one, rewriting its history
      • Often done with squashing (combining multiple commits into a single commit) on topic branches before merging with master to simplify the history
      • Because it rewrites history, you shouldn't do it on branches shared with other developers
      • git rebase <new-base>
      • After a rebase, it's easy to do fast-forward merges
      • git rebase -i starts an interactive rebase, and lets you specify what to do with each commit. git rebase --abort let's you stop it mid-way through.
      • If you need to squash the last few commits, you can use git rebase -i HEAD~2 for example.
    • gh-pages