Git and GitHub Training

I went today to a Git/GitHub training organized by Canoo and lead by Tim Berglund (GitHub.com) The online training presentation is available at http://teach.github.com/presentations/git-foundations.html use first left key then left/right/up and bottom keys to navigate through the slides.

My notes are still under reviews, but are available at http://gittraining.waltercedric.com

GitHub also offers free, short, topical online classes about GitHub, Git and the union of these two technologies Here.

GIT training

• Tim Berglund
  • ~ http://timberglund.com/

    ~ https://twitter.com/tlberglund

    ~ https://github.com/tlberglund

    Online Slides

    • http://teach.github.com/presentations/git-foundations.html#/
• config
  • global
    • user level config for logged in user
  • local
    • use when pushing to github later
  • system
    • apply to every user logged in on the machine
  • Git autodetect file type
    • binary
    • text
      • CRLF
        • dont mess with it if it is working

        #Colorize console output for legibility
        git config –global color.ui auto

        #Force files to be LF in the repo, even on Mac/Linux
        git config –global core.autocrlf input

        #Force Windows to convert to CRLF
        # on checkout and to LF on `add`
        git config –global core.autocrlf true

  • Git Help
    • git help config
      • To print and read
• 1. Staging area
  • first add
    • git init newproject
    • cd newproject
    • vi caesar.txt
    • git status
      • file red
        • untracked
        • modified
    • git add caesar.txt
      • file green = tracked
      • it is now in staging
    • refs are name for objects
      • ex master
    • modifiy the file
      • vi caesar.txt
    • file has to go to staging before being committed
      • git add caesar.txt
        • go in staging
        • when in staging the file has no refs
      • git commit -m “small change”
        • now has a name associated to it
  • Why
    • so you can work on paralell files or topics
      • is it not a bad sign?
    • you can also commit then later “part” of the file
      • you could break easily since unit test may be broken with half file
    • advance command
      • revert
        • not like subversion
      • cherry pick
      • only if you know what it is in your stagign area
• 4. Branching
  • HEAD
    • equals to most recent commit
    • is going to be the parent of the next commit
    • it is where the branch live
    • master is just another branch
    • a branch is at least 2 commit with the same parent
  • branch is fast because it is local
  • Play
    • create a branch
      • git branch feature
      • this do not switch to the branch
    • move to branch
      • git checkout feature

        check where you are working

        • git branch
        • git status

        vi caesar.txt

        git add caesar.txt

        git commit -m “add a title”

        git lg

        • 
    • merge feature to master
      • git checkout master
      • git merge feature
        • 
      • and kill that branch
        • better not used it if its a feature
  • git reset
    • if we discover an error in commit message 259a4c9
    • hard
      • reset both master and any branch
        • like merge has never happen
        • blow up old commit and create new ons!
        • dangerous you can lose code
    • Play
      • git reset –hard 259a4c9
      • git commit –amend
        • commits are lost
          • you can not find it
          • still there as an object but has no refs!
          • you have to remember the hash
          • may be garbage collected after 60 days
          • git reflog
            • may be still in there
      • you can then redo a git merge feature
    • better use rebase
      • 95% of git users dont know how
      • quite advanced
  • git branch adopted 259a4c9
    • create a branch adopted of the amended commit
  • delete the branch
    • git branch -d feature
      • delete the label of the branch
      • but the commit stay of course
    • git branch -d adopted
      • will complains as not merged
      • force the delete of non merged
      • git branch -D adopted
• 5. merge conflict
  • GIT search for chunk that are similar and can merged automatically
  • Play
    • git merge feature
    • git status
      • show merge conflict
  • if you know what is in reflog
    • git reset –hard [email protected]{1}
    • you can undo last command
    • not always 1 command lead to only one entry in reflog
    • use with precaution
  • external merge tool
    • p4merge
      • config
        • git config –global merge.tool p4merge
        • git config –global mergetool.prompt false
        • git config –global mergetool.keepBackup false
        • git config –global mergetool.keepTemporaries false
      • use
        • git mergetool
  • to solve merge conflict on binary file
    • automatic merge not possible
    • you can decide your or theirs is the right one
    • git checkout –theirs — animated.gif
      • git add animated.gif
        • git commit -m “use their version of binary animated.gif”
• 7. GitHub
  • git remote add origin https://xxxxx/yyyy.git
    • create a local config at .git/config
    • origin is a convention name
  • git push
    • push unique content to remote
    • git push -u origin master
      • -u to make master

        remember that it

        track remote origin

    • git branch -a
      • now display also remote branch in red
  • git help daemon
    • share

      to start a git server

      to server your local

      git repo as a remote

      for colleagues

  • git help bundle
    • no network?

      write objects and refs into files

      for sharing on cdrom or

      shared drive

      for highla secure environment

      without network: ex military

  • git fetch
    • get all objects, blobs and commit

      but do not change master

      • just get and save commits

        in local remote area (read only)

        git checkout feature5

        • feature5 being in remote origin
        • will create a local branch feature5
  • git pull
    • do a git fetch and merge into master
  • git push
    • need no parameter but use push.default if it exist
    • every local branch will be pushed as default if none have been specified
    • use
      • git config –global push.default simple
        • to only push the branch where you have
        • set it if you dont know te default
      • git help config
        • upstream
        • simple
        • …
    • when pushing failed
      • failed to push some refs upstream

        because there is a new commit

        in master which is ahead of mine

        fast forwards will work

        only if i have new stuff

        • git pull (make a merge)

          git push

          better would have been to

          make a rebase also to clear

          the noise of merging to push

  • Fun
    • ~ http://octodex.github.com/
• 9. Collaborating
  • Play
    • git config –global credential.helper cache
      • work only in linux/mac

      vi cedric.txt

      git add .

      git commit -m “add file”

      git push

      • if not succed do a git pull

      gitk –all

      • see a lot of noise because

        of merge done by pull before

        each push

      force to rebase on pull is a

      good idea to remove noise

      • git config –local branch.master.rebase true
      • or better
        • git config –global branch.autosetuprebase always
  • tags
    • 3 differents
      • reference
        • git tag XXXXX hash
          • it is a reference
          • always point to commit
      • annotated
        • -a –annotate Make an unsigned, annotated tag object
        • git tag -a ANNOTATED_TAG
        • is an indirection to a tag
      • …

      tags are not pushed

      by default to origin

      • git push
        • do nothing
      • git push origin ANNOTATED_TAG
        • push a specific tag
      • git push –tags
        • push all tags

      delete

      • a tag
        • git tag -d tagname
      • a branch
        • git push –delete origin branchname
        • git push origin :branchname
• revealJS
• filesystem
  • Hooks
    • entry point to hook
  • refs
  • objects
  • HEAD
    • commit youre on
• 2. Log history
  • # git log
  • hash
    • 40 character hash
  • git log –format= email
  • git log –format=raw
    • useful for training
    • relationship tree -> parent -> author -> committer
      • it is a graph
        • important to understand
      • git log –graph
      • git log –graph –decorate –format=oneline
        • still a lot of hash
      • git log –graph –decorate –format=oneline –abbrev-commit
  • git log –patch
    • Show all history with patches
  • aliases
    • git lol
      • git config –global alias.lol “log –graph –decorate –oneline –all”

        http://boyen.github.com

        • like a puppet for developer

        

    • git lg
      • git config –global alias.lg “log –graph –pretty=format:’%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset’ –abbrev-commit –all”
• 3. Diff
  • git diff
  • git diff –staged
    • what is my next commit will do?
  • git diff –word-diff
    • 
  • git diff HEAD
    • show changes between local and something in history
  • create scripts
    • ~/scripts/git-xxxxxx
    • ~/scripts/git-log
  • git log ec7674 -1 –patch
    • to look at a particular commit and its diff
  • git show ec7674
• 4. move and rename
  • remove a file from VCS and keep local copy
    • git rm –cached — <filename>
    • git commit -m “remove from vcs”
  • GIT integrity check
    • each commit contains at least one tree and one or more blobs
    • content is king
    • blobs
      • store file content
      • no permissions
      • no metadata
      • each blob is stored under first 2 character of hash directory in /objects
      • every change of a file create a NEW blob
        • diff is calculating the diff on demand

          not storing them like svn

    • tree
      • contains file name
      • references to one or many blobs
      • one to n tree in a commit
    • git pack
      • all commits can get packed to find similar blob
      • 5 to 10 times less space than SVN
    • git GC
      • find all commits, trees and blobs

        that can not be accessed and remove them

  • git add -u .
    • update only tracked file not moved/renamed  file
    • use instead
      • git add -A .
  • git checkout — file3.txt
    • revert file content
  • similarity content analyser
    • if more then 50% then it count the the file as renamed otherwise it is new
    • git log -2 –stat
      • may show delete + add for a move operations
    • git log -2 –stat -M
      • display also similarity index
      • may show move correctly
      • git log -2 –stat -M90
        • with 90% similarity threashold
      • git log -2 –stat -M — file3.txt
        • limit to file
      • git log -2 –stat -M –follow — file3.txt
        • changes + move + create
• 6. Rebase
  • interactive rebase
  • rewrite the history
    • changing authors or any other properties
  • preparation for merging
    • Rebase Rebase Fastforward
      • ex: to make my code changes in branch

        appear like a continuation of master

        • d19′ = d19
        • e69′ = e69
        • but still different commits!

        do it in branch

        you want to move

        • git rebase master
          • change shape of the graph

            keep timestamp and author

            pull of all commits of a branch &

            replay all commit in master

            • may create small conflicts

        make the history straightforward

        • especially if you have a lot of branches
          • otherwise look like a train station
        • but you hide informations
          • from which branch it was merged
    • non fastforward
    • history
      • is a graph not a list like in “git log”
      • it is not temporal but topological
  • interactive rebase
    • to group commits into one
      • “commits are stories not just checkpoints”
    • git rebase -i [start, end]
      • start = HEAD as default
      • end = hash
      • git rebase -i HEAD^
        • parent of head
        • you can combine HEAD^^^^^^
      • git rebase -i HEAD~10
        • last 10 commit
      • git rev-parse HEAD^
        • give hash
      • git help gitrevisions
        • adavnce list of expressions
      • create a file so you can decide what to do
        • has command
        • pick, reword, edit,squash, fixup and exec
        • you can not squash the oldest commit
• 8. Forking
  • Play
    • git clone xxxx
    • vi xxxxx.txt
    • git add .
    • git commit -m “”
    • git push
    • open a pull request
  • pull request
    • invitation to start a conversation
    • add metadata
      • screenshots
      • emoji-cheat-sheet.com
    • is an iterative process
      • threaded discussion
  • ideas
    • when opening  a feature branch
      • create a pull request immediately
      • improve communication and awareness and start discussion
      • even if there is no code yet done
  • merge conflict can not be solved in github
    • has to be done in command line