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Changes
→Week 4
** Relationship of <code>git commit</code> with branches
*** commit SHA: <code>e0ee2b5acd01acbe5b0bc1ee24b73e5d53a1fd70</code> or shortened to <code>e0ee2b5</code>
*** <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>
*** <code>master</code> branch vs. "Topic Branches": '''all work happens on a new branch'''
** 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 checkout <branch name | commit SHA></code>, discussion of "detated 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 or reset, checkout new branch)
** 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
*** <code>git checkout master</code> - switch to master branch
**** 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 <code>git pull</code> does a <code>git fetch</code> and <code>git merge</code> 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 <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
