a brief introduction to working with git
DESCRIPTION
This slide deck is intended for Git beginners and focuses on the underlying concepts, the usage of the command line, especially the commands git reset, git checkout, git revert, git commit, and eventually introduces models for using Git and why git rebase may play an important role in some those models.TRANSCRIPT
Business Informatics GroupInstitute of Software Technology and Interactive Systems Vienna University of TechnologyFavoritenstraße 9-11/188-3, 1040 Vienna, Austriaphone: +43 (1) 58801-18804 (secretary), fax: +43 (1) [email protected], www.big.tuwien.ac.at
A Brief Introduction to Working with Git
10.03.2014VUT, Vienna, Austria
Philip Langer
History of Versioning Systems
Based on http://codicesoftware.blogspot.com/2010/11/version-control-timeline.html
local to central …
central to distributed …
1972
sccsdiscourage branching … everything is a branch …
3
Git: A Distributed Versioning System
There is no single repository server Every peer is a full repository instance
Single-peer versioning possible Including the complete history Committing changes is independent of peers Allows disconnected operation
Collaboration is done by pushing/pulling commits Comparable to peer-to-peer networks The role of peers is purely organizational
No technical difference among peers Single common central server possible
One peer happens to be the central repo But several other architectures are possible too
Gate-keeper architecture Teams of teams
commit
push & pull
push & pull
push & pull
<Bob>
<Alice>
<Sally>
<Server>
<Harry>
push & pull
4
The Four Layers & Transferring Changes Among Them
Every repository consists of a Workspace Index (“staging area”) Local repository Remote repositories …
Transferring changes git add
workspace to index git commit
index to local branch git push
local branch to remote branch …
Changes are organized in commits Each commit has a parent The history is basically a DAG
5
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
6
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
7
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
8
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard HEAD~
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
9
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard HEAD~
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
!
10
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
11
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
Reset index after wrong
add
12
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed] HEAD~
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
13
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed] HEAD~
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
Undo last commit, however
it‘s still there
14
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
Does nothing actualy
(HEAD is default)
15
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft HEAD~
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
16
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is HEAD? A reference pointing to the last commit (of the current branch) Thus, it will be the parent of the next commit Relative commit expressions e.g. with HEAD~2
git reset [--soft | --mixed | --hard] [commit | reference to commit] Resets HEAD in history, index, and/or workspace to [commit] git reset --hard
History, index, and workspace git reset [--mixed]
History and index git reset --soft HEAD~
Only history …
default:HEAD
default:--mixed
History
Index
Workspace
Head
Undo last commit, leaving index untouched
17
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is checkout? Get a version from the history And overwrite workspace (also for creating and changing branches … later)
git checkout -- <file/s> Get version of <file/s> from HEAD Overwrite version in workspace
History
Index
Workspace
Head
Undo last commit, leaving index untouched
18
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is checkout? Get a version from the history And overwrite workspace (also for creating and changing branches … later)
git checkout -- <file/s> Get version of <file/s> from HEAD Overwrite version in workspace
History
Index
Workspace
Head
Undo local changes to workspace.
!
19
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is revert? Does not modify history (good if you pushed already) Takes a commit from history Creates reverse patch Commits reverse patch (new commit)
git revert HEAD~1
History
Index
Workspace
Head
Must be clean!
20
Before talking about branches…Demystifying “git reset”, “git checkout”, and “git revert”
What is revert? Does not modify history (good if you pushed already) Takes a commit from history Creates reverse patch Commits reverse patch (new commit)
git revert HEAD~1
History
Index
Workspace
Head
Undo commits after you‘ve already pushed them.
Must be clean!
21
Branching
After all every change (local or remote) is a fork leading to a new branch So make branches a first-class concept No logical difference between local and remote branches Every merge is a branch merge
<Bob>
<Server>
<Alice>
22
Branching
Each commit has a parent A branch is nothing more than a pointer to a commit
CurrentBranch
23
Branching
Each commit has a parent ( DAG) A branch is nothing more than a pointer to a commit
24
Branching
Local branches may link to “tracking branches”
CurrentBranch
25
Branching
Branches can be linked in ./git/config(links are also created automatically in certain cases;or may be linked explicitly using git checkout --track)
[remote "origin"]fetch = +refs/heads/*:refs/remotes/origin/*url = https://code.google.com/a/eclipselabs.org/p/moliz/
[branch "master"]remote = originmerge = refs/heads/master
[branch "issue_18_alf"]remote = originmerge = refs/heads/issue_18_alf
26
Merging Branches
git checkout mastergit merge iss53
27
Merging Branches
git checkout mastergit merge iss53
Note that git pull is a git fetch & git merge
28
Branching Models of Git
Several different “models” All entirely organizational
The svn-like model: Only one branch Only one central repo git pull (origin master) Apply changes git commit (master) git push (origin master) Good for e.g. papers
The isolated-development model Own branch for current dev Own branch for releases Own branch for each feature
29
Keeping the History of Topic Branches Clean: Rebase
git checkout experiment… // apply changesgit commit -agit checkout mastergit merge experiment
30
Keeping the History of Topic Branches Clean: Rebase
git checkout experiment… // apply changesgit commit -agit checkout mastergit merge experiment
31
Keeping the History of Topic Branches Clean: Rebase
git checkout experiment… // apply changesgit commit -agit rebase master
Rebase is rewriting history! Never rebase pushed history!
32
Keeping the History of Topic Branches Clean: Rebase
Improving previous commits… // apply changesgit commit -a… // apply changesgit commit -agit rebase -i HEAD~2
# Rebase 710f0f8..a5f4a0d onto 710f0f8## Commands:# p, pick = use commit# e, edit = use commit, but stop for amending# s, squash = use commit, but meld into previous commit