Mastering Git Basics - erlang-factory.com · Mastering Git Basics by Tom Preston-Werner Presentation ... (C5) is created Presentation

Mastering Git Basicsby Tom Preston-Werner

Presentation http://test.smackaho.st:9090/onepage

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@mojombo


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Before we start...


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Forget everything you know

about version control


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Installing Git


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Mac

Git OSX Installer

Homebrew

MacPorts

Manually


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Linux

Apt

Ports

Yum

Manually


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Windows

msysgit


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help.github.com


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Initial Configurationhttp://gist.github.com/340818

$ git config --global user.name "Tom Preston-Werner"$ git config --global user.email "[email protected]"

$ git config --global color.ui true


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Creating and Committing


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Make a directory for your new project $ cd path/to/repos $ mkdir hello $ cd hello


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Working directory


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git init $ ls -al # dir is empty $ git init # initialize git repo $ ls -al # new .git dir


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Behold the index!


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Write some code $ vim hello.sh $ vim goodbye.sh


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git add$ git add hello.sh # add content to index$ git add goodbye.sh # add content to index


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Index now contains working dir content


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git statusShow the status of index and working dir

$ git status


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git commit $ git commit # make a commit


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A commit is a snapshot taken from the index

NOT THE WORKING DIRECTORY


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git logPrint a log of commits

$ git log


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RecapThe current state of the repo


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Make some ambitious changes $ vim hello.sh # modify the file


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Working dir now contains D0: a delta from C0


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Review the changed files $ git status


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git diffShow diff between index and working dir

$ git diff


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D0 = Diff(Index, WorkingDir)


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git add -pInteractively add changed hunks

$ git add -p


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D0 is now in working dir AND index


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git diff now shows nothing!Where did it go?


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git diff --stagedShow diff between commit and index

$ git diff --staged


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D0 = Diff(Commit, Index)


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git commit -mCreate a commit with the given commit message $ git commit -m "more ambition!"


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Commit is rolled from index


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Remember:

Make changes to working dir1.

Stage those changes to the index2.

Commit the current state of the index3.


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RecapTwo commits, C0 and C1


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Every commit has zero or

more parent commits


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Branching and Merging


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git branchShow all local branches

$ git branch


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The default branch is named

master


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Branches are just pointers to commits


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It's easiest to think of the working

directory as corresponding to a branch


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As you commit, the branch moves with you


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git branchCreate a new branch pointing at

the current commit $ git branch uppercase


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A new branch has been created

but the working dir has not changed


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git checkoutSwitch working dir to the given branch

$ git checkout uppercase


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Working dir now corresponds to uppercase


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Convert the string to uppercase

on this branch and commit the change$ vim hello.sh$ git add -p$ git commit -m 'convert string to uppercase'


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Branches have now diverged!


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git branch -vShow branches and the commits they point to $ git branch -v


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Switch back to the master branch.

Notice that working dir has been changed.$ cat hello.sh # uppercase version$ git checkout master$ cat hello.sh # master version


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Working directory is now consistent

with the master branch


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git diff R1 R2Diff between two arbitrary commits

$ git diff master uppercase


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Show the work done between branches


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git mergeMerge the given commit into the current branch $ git merge uppercase


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Both branches now point at the same commit


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This kind of merge is known as a

fast-forward merge because the

merged branch was a direct descendent


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git branch -dDelete the given branch

$ git branch -d uppercase


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Only the pointer has been deleted


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What if both branches have commits?


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git checkout -bCreate a new branch and switch to it

$ git checkout -b greeting


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Modify the greetings; commit;

and switch back to master $ vim hello.sh $ vim goodbye.sh $ git add -p $ git commit -m 'new greetings' $ git checkout master


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Create a new file on master

and attempt to add it $ vim README $ git add -p # nothing to review! $ git status # find out why


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File trackingGit remembers what files have been added.

New files must be explicitly added.


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Add the contents of the new file $ git add . # add everything! $ git status # see that it worked


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Oops, we forgot something... $ vim README $ git status # make sure


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Two deltas have been introduced


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Inspect the deltas, and continue $ git diff --staged # old change $ git diff # new change $ git add -p # add again $ git commit -m "add a readme"


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Recap of forked lineage


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Merge greeting into master $ git merge greeting


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A new merge commit (C5) is created


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This kind of merge is known as

a recursive merge and

uses a 3-way merge strategy


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Three way (recursive) merge strategy


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git log --graphShow the commit log with graph structure

$ git log --graph


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The power of Undo


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First, a word about referencesA reference is a way to refer to a commit


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Examples:

5c673e53912d86eb771ee0ab0c678ecffa4b939c

5c673e5

master

HEAD

HEAD^^


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HEAD is a dynamic reference that

follows your current checkout


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Ancestry reference modifiers


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git reset --hardReset a branch and working dir

$ git reset --hard head^


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master is now pointing to C4.

C5 still exists, but is dangling.


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git reflogShow previous values of HEAD

$ git reflog


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What about merge conflicts?


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Modify a line that was also changed

in the greeting branch $ vim hello.sh $ git add -p


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git commit --amendModify the content of the last commit

$ git commit --amend


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Attempt to merge greeting $ git merge greeting


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Cleanly merged files are staged.

Conflicts are left in working dir. $ git diff --staged # clean $ git diff # dirty $ git status # summary


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Clean up the mess; use git add to mark

a conflicted file as properly merged.

Commit to seal the deal. $ git add hello.sh $ git commit


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Collaboration


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Back to your repos directory $ cd ..


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git cloneClone a repository

$ git clone hello helloclone $ cd helloclone


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You can also clone from remote repositories


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git remoteDisplay a list of remotes

$ git remote -v


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git branch -aShow all branches (local and remote)

$ git branch -a


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Assume that upstream makes a commit

on the master branch


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Current state of upstream


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git fetchFetch commits from the given remote

$ git fetch origin


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Remote commits have been downloaded,

but have not affected your local branches


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View the changes in the upstream

origin/master branch $ git diff head origin/master


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Comparing unmerged upstream commits


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Merge the upstream origin/master branch

into your local master branch $ git merge origin/master


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The upstream commits have been merged


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What if you want to share your changes?


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Assume a new branch fi x with a commit


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git pushPush some commits to a remote

$ git push origin fix


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Remote now contains the fi x branch!


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Now others that have access to the remote

can fetch and work on the fi x branch


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Collaboration in Git is all about moving

commits around between repositories


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Where do I go from here?


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Pro Git by Scott Chaconhttp://progit.org


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Thanks!


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Mastering Git Basics - erlang-factory.com · Mastering Git Basics by Tom Preston-Werner Presentation ... (C5) is created Presentation