How Not To GITLucas Gomes <@x8lucas8x>

Agenda● Who am I?● GIT Anti-Patterns

○ Manual Merging○ Copy-Paste Backup○ Dumb Bug Hunting○ Dumb Conflict

Resolution○ Jumbo Commit

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○ Messing with History○ Divergent Master○ Self Reviewing

● References● Q & A

Software EngineerPassionate Hacker ArchLinux ZealotFOSS Enthusiast

Startups, Big Data,AI, NoSQL, Python,C++/Qt, Git, Groovy,Cloud, IoT, and allthat jazz.

Lucas Lira Gomes

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GIT Anti-Patterns4

Manual Merging

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$ git checkout branchA...$ git commit...$ git pull origin master...$ echo ‘No pull requests this time!’...$ git checkout master...$ git rebase branchA...$ git push origin master...

Manual Merging

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● Problems○ “To Err is Human”

■ Automate what you can○ Permission management

■ Higher friction○ Jeopardise collaboration

■ Less code-review

Manual Merging

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A’sLocal

B’sLocal

C’sLocal

CentralRemote

Shared Repository

Manual Merging

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A’sLocal

B’sLocal

CentralRemote

A’sRemote

B’sRemote

ForkPull

Manual Merging

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● Solution○ Fork & Pull model

■ Use proper tools○ Avoid manual

merges/rebases■ Default to pull

requests

Manual Merging

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● Solution○ Fork to access

■ Create it first

$ git clone git@server_url:my_fork/remote.git

Manual Merging

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● Solution○ For updates

■ Forbid pushes■ Set up read-only

remote

$ git remote add central https://server_url/central/remote.git$ git remote set-url central --push "You shall NOT push!!!"

Copy-Paste Backup

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$ git status# On branch master# ...# modified: index.html#...$ cp index.html backup_index.html...$ git checkout -- index.html...$ git checkout branchBSwitched to a new branch 'branchB'

Copy-Paste Backup

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● Problems○ “To Err is Human”

■ Use proper tools

Copy-Paste Backup

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● Solution○ Stash it

$ git stashSaved working directory and index state "WIP on master: 049d078 added the index file"HEAD is now at 049d078 added the index file (To restore them type "git stash apply")

Copy-Paste Backup

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● Solution○ Stash it

$ git status# On branch masternothing to commit, working directory clean

$ git stash liststash@{0}: WIP on master: 049d078 added the index file

Copy-Paste Backup

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● Solution○ Stash it

$ git stash apply# On branch master# Changes not staged for commit:# (use "git add <file>..." to update what will be committed)## modified: index.html

$ git stash drop stash@{0}Dropped stash@{0} (364e91f3f268f0900bc3ee613f9f733e82aaed43)

Dumb Bug Hunting

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$ git commit...$ git commit...$ git commit...$ run app.py FATAL ERRORGonna cry?...$ diff HEAD~12...$ vim app.py...

Dumb Bug Hunting

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● Problems○ Not efficient○ More changed code

==More difficulty

Dumb Bug Hunting

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● Solution○ Manually Bitsec

$ git bisect start$ git bisect bad BAD_SHA1_HASH$ git bisect good GOOD_SHA1_HASHBisecting: 6 revisions left to test after this[b047b02ea83310a70fd603dc8cd7a6cd13d15c04] secure this thing

Dumb Bug Hunting

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● Solution○ Manually Bitsec

$ git bisect goodBisecting: 3 revisions left to test after this[b047b02ea83310a70fd603dc8cd7a6cd13d15c04] secure this thing

$ git bisect badBisecting: 1 revisions left to test after this[f71ce38690acf49c1f3c9bea38e09d82a5ce6014] drop exceptions table

Dumb Bug Hunting

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● Solution○ Manually Bitsec

$ git bisect goodb047b02ea83310a70fd603dc8cd7a6cd13d15c04 is first bad commitcommit b047b02ea83310a70fd603dc8cd7a6cd13d15c04Author: User1 <user1@example.com>Date: Tue Jan 27 14:48:32 2015 -0800...

Dumb Bug Hunting

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● Solution○ Automate Bitsec

$ git bisect start BAD_SHA1_HASH GOOD_SHA1_HASH$ git bisect run make test arguments...

Dumb Conflict Resolution

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$ git pull origin master...$ git status# On branch branchA# You have unmerged paths.# ...# both modified: README.md#...$ vim README.md...

Dumb Conflict Resolution

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● Problems○ Not efficient○ Prone to typing errors

Dumb Conflict Resolution

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● Solution○ Use mergetool

$ git config --global merge.tool YOUR_DIFF_VIEWER

Dumb Conflict Resolution

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● Solution○ Use mergetool

$ git mergetoolMerging the files: README

Normal merge conflict for 'README': {local}: modified {remote}: modified

Hit return to start merge resolution tool (kdiff3):

Dumb Conflict Resolution

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● Solution○ Use mergetool (KDiff3)

Dumb Conflict Resolution

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● Solution○ Use mergetool (Meld)

Dumb Conflict Resolution

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● Solution○ Use mergetool

■ emerge■ gvimdiff■ vimdiff

Jumbo Commit

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$ git add src/views/....$ git add src/models/....$ git add src/delegates/....$ git add images/....$ git commit -a ‘Biggest commit ever!’...

Jumbo Commit

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● Problems○ Long-term results

■ Team○ Review procrastination

■ Higher cognitive load○ Pulls are more prone to

conflict

Jumbo Commit

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● Solution○ Divide and conquer

■ Create granular commits

Messing with History

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$ git pull origin master...$ git log...$ git commit --amend...$ git push origin master...# ! [rejected] master -> master (non-fast-forward)...

Messing with History

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● Problems○ Cannot push○ If forced (push -f)

■ Break others history

■ Lose commits

Messing with History

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● Solution○ Avoid messing with

pushed history■ On shared

repositories only

Messing with History

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● Solution○ Use Git Revert

$ git revert DESIRED_SHA1_HASH

Divergent Master

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$ git checkout master...$ git rebase branchA...$ git status...# Your branch and 'origin/master' have diverged...

Divergent Master

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● Problems○ Prone to mix different

branches commits■ Master is the

ramification point

Divergent Master

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● Solution○ Use master as a carbon copy

$ git checkout -b branchASwitched to a new branch 'branchA'

$ git branch -D master...

Divergent Master

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● Solution○ Use master as a carbon copy

$ git branch -abranchAremotes/central/master

$ git checkout remotes/central/master...

Divergent Master

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● Solution○ Use master as a carbon copy

$ git checkout -b masterSwitched to a new branch ‘master’

Self Reviewing

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$ git push origin branchA...$ echo “Lets create a pull request!”...

Self Reviewing

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● Problems○ Team specialisation

■ “Not my code"○ Less opportunity

■ Learning■ Training

Self Reviewing

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● Solution○ Assign pull requests

to others

References1. https://www.git-scm.com/2. http://www.atlassian.com/git/tutorials/

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How Not To GITLucas Gomes <@x8lucas8x>