Git Panic

and how to avoid it

Cool tricks you learn
if you actually read the manual

About me:

• Hi, I'm Mihail Mikov
• Full-stack engineer at Skyscanner
• Hobby juggler

          git config --global user.name  "Mihail Mikov"
          git config --global user.email "mmikov@aubg.edu"
        

Git is hard

Git Panic symptoms

• Fear of the console / GUI only
• Unstructured / messy history
• Complicated / blocking workflow
• Fixing git by cloning to a new repo

Git Panic symptoms

• Push races / lots of conflicts
• Lost local changes
• Lost remote commits

So, how do I fix my git?

Bad solution: Panic

Solution

Pure Vegan Homeopathic solutions

• Read the manual
• Use the console
• Check your status and history often
• Fetch remotes often
• Push your WIP often

Pure Vegan Homeopathic solutions

• Follow a commit message format
• Name remotes and branches meaningfully
• Make git help you:
  • Aliases
  • Tags
  • Hooks
  • Command options

About commands

          commandName --options arguments
        

Command scope

Project history

          git log --all --graph --format="%h %d %an %cr %s"
          git log --author="Your Name" --since="3 weeks ago"
          git log master...my-branch --left-right
          git log --stat -p
        

Commit ranges

Branch history

          # show a history of the commits
          # the given branch was pointing to
          git reflog <branch>
        

Referencing commits

          # exclude commit and its ancestry
          ^master

          # the 2nd ancestor of the given commit
          master^^
          master~2

          #the 2nd parent of the current commit
          master^2
        

Referencing refs

          # the 3rd commit in the log of the ref
          master@{2}

          # the commit the ref pointed to at the given date
          master@{5.days.ago}
        

File history

          # show who and when last modified each line of a file
          git blame --date=relative <file-name>

          # show the detailed history of a file
          git lg -p -- <file-name>
        

Adding something specific

          git add -p
        

Clearing the index snippet by snippet

          # unstage changes from the index
          git reset -p
        

Make that snippet great again

          # pick and override snippets in the working tree
          git checkout -p <commitish> <file-name>
        

Checkout the code

          # checkout a branch you previously worked on
          git checkout @{-1}

          # create a new branch and switch to it
          git checkout -b "new_branch"

          # like "-b" creates a branch, but the first commit
          # on this branch will start an independant history
          git checkout --orphan "separate_history"
        

Detached head

          git checkout <branch>
          # HEAD is pointing to a branch
          # which is pointing to a commit

          git checkout <commit>
          # HEAD is pointing directly to a commit
        

Unpacking commits

          # make HEAD point to a specific commit
          # without changing the index or the working tree
          git reset --soft <commitish>
        

Moving our HEAD around

          # both HEAD and the current branch
          # will point to the given commit
          git reset --hard <commitish>
        

Undo some changes

          # creates a commit that negates the changes
          # introduced in another commit
          git revert <commitish>
        

"Moving" a single commit around

          # creates a new commit at HEAD with the
          # same changes introduced by another commit
          git cherry-pick <commitish>
        

"Moving" many commits around

          # as if you cherry-picked
          # all the commits on a brach in order
          git rebase <new-base> <target-defaults-to-HEAD>

          # interactive rebase
          git rebase -i

          # rebase instead of creating a merge commit
          git pull --rebase
        

Rebase in action

Setting up Aliases

          git config --global alias.co "checkout"
          git config --global alias.br "branch --verbose"
          git config --global alias.up "pull --rebase"

          git config --global alias.lg
            "log --graph --format='%h %d %an %cr %s'"

          git config --global alias.quickfix
            "commit -p --amend --no-edit"
        

Conflicts? Just ignore 'em

Resolving conflicts

          # abort if you can't solve the conflicts
          git <merge | rebase | cherry-pick> --abort

          # Warning: the meaning of --theirs / --ours
          # is different between merge and rebase

          # finish the operation with "--continue"
          git add <resolved-files>
          git <merge | rebase | cherry-pick> --continue
        

Common workflows

• All in master
• Team / Feature branches
• Merge / Pull requests

Fetch, compare, rebase

          git fetch <remote> <branch>

          # show a graph of all commits
          # since the last common point between the branches
          git lg --left-right HEAD...<remote/branch>

          # rebase your changes on top of the remote
          git rebase <remote/branch>
        

Safe force push

          # only re-write the remote's history
          # if you already have a local copy of it
          git push --force-with-lease

          # alias: git sfp
        

Merge, but no fast-forward

          # Rebase and merge to keep the branch history visible
          git rebase feature_branch master
          git merge feature_branch --no-ff
        

Recap & takeaways

• Use the console
• Name remotes, branches and commits meaningfully
• Keep your workflow & history understandable
• Fetch and push often
• Read the manual
• Make git help you

Links:

• Learn git in the browser
• Git tutorials by Atlassian
• A visual guide to git
• Git from the inside out
• Git from the inside out (youtube)
• Git internals
• Git configuration tips & tricks
• The code of this presentation on github

Questions?!

Thank you!