git Basic concepts and usage Francis Colas What is git? git concepts Standard commands Feature branch workflow Conclusion 2 – Francis Colas – git basics 01 What is git? What is git? Revision control Source code: I everything is source code, I usually written in an iterative process, I sometimes by several persons; Revision control: I management of versions of documents, I tracking of changes, I restoration of previous state, I similar concepts to a database; Some generic concepts: I atomicity: ensuring consistency of state, I distributed/centralized: communication model of changes, I branches and tags: development direction and milestones, I locking/merging: handling of concurrent changes. 4 – Francis Colas – git basics What is git? History of git Timeline: before hand-numbered or date-stamped copies, 1990 CVS: centralized and non atomic, 2000 Subversion: centralized and atomic, 2000s GNU Arch, Monotone, Darcs: decentralized and atomic, 2005 Linux cannot use BitKeeper anymore, 2005 answer: mercurial and git. 5 – Francis Colas – git basics 02 git concepts git concepts General characteristics Repositories: I monolithic and self-sufficient, I everybody has a full clone, I in particular: no need for a connexion to commit. Concepts: I git handles files (no empty directory), I central objects are commits: I set of file changes,1 I applied on top of a given [list of] commit[s], I tags and branches just point to a commit, I remotes are pointers to other clones (github, gitlab, other clone somewhere...). 1actually, they are more a snapshot of the state 7 – Francis Colas – git basics git concepts Staging area Three (conceptual) places: I working directory: the files in the filesystem, I staging area: the files as how they’ll be committed, I git repository: committed files. What it means: I changes happen in working directory, I need for preparation of the commit using the staging area, I actual commit is a frozen snapshot of the staging area. 8 – Francis Colas – git basics 03 Standard commands Manipulating the staging area: I git add <files>: add current state of files to next commit, I git rm <files>: delete files, I git mv <oldname> <newname>: move/rename a file. Looking at status: I git status: list state of working copy with respect to last commit. Commit and transmission: I git commit -m "commit message": record changes into a commit, I git pull [<url|remote>]: get changes and merge them, I git push [<url|remote>]: sends commit to remote/url. Standard commands Basic commands Initialization: I git init <name>: initialize an empty repository , I git clone <url>: clone a repository, 10 – Francis Colas – git basics Looking at status: I git status: list state of working copy with respect to last commit. Commit and transmission: I git commit -m "commit message": record changes into a commit, I git pull [<url|remote>]: get changes and merge them, I git push [<url|remote>]: sends commit to remote/url. Standard commands Basic commands Initialization: I git init <name>: initialize an empty repository , I git clone <url>: clone a repository, Manipulating the staging area: I git add <files>: add current state of files to next commit, I git rm <files>: delete files, I git mv <oldname> <newname>: move/rename a file. 10 – Francis Colas – git basics Commit and transmission: I git commit -m "commit message": record changes into a commit, I git pull [<url|remote>]: get changes and merge them, I git push [<url|remote>]: sends commit to remote/url. Standard commands Basic commands Initialization: I git init <name>: initialize an empty repository , I git clone <url>: clone a repository, Manipulating the staging area: I git add <files>: add current state of files to next commit, I git rm <files>: delete files, I git mv <oldname> <newname>: move/rename a file. Looking at status: I git status: list state of working copy with respect to last commit. 10 – Francis Colas – git basics Standard commands Basic commands Initialization: I git init <name>: initialize an empty repository , I git clone <url>: clone a repository, Manipulating the staging area: I git add <files>: add current state of files to next commit, I git rm <files>: delete files, I git mv <oldname> <newname>: move/rename a file. Looking at status: I git status: list state of working copy with respect to last commit. Commit and transmission: I git commit -m "commit message": record changes into a commit, I git pull [<url|remote>]: get changes and merge them, I git push [<url|remote>]: sends commit to remote/url. 10 – Francis Colas – git basics Standard commands Branching commands Handling branches (because it’s cool): I git branch <branch>: create branch, I git branch -d <branch>: delete a branch, I git checkout <branch>: change to a different branch, I git checkout -b <branch>: create and change to branch, I git push -u <remote> <branch>: create and push branch to remote, I git merge <branch>: merge changes of the given branch into the current one (used by pull). 11 – Francis Colas – git basics Standard commands Additional information Temporary changes: I git stash: save current changes aside, I git stash pop: restore saved changes. Seeing branches and commits: I gitk [--all]: good tool when lost in branches, I git gui: makes it easy to pick individual changes in a file. Ignore file: I .gitignore: list of patterns of filenames that will be ignored. Fixing the last commit before sending it: I git commit --amend: replaces commit with current staging area. 12 – Francis Colas – git basics 04 Feature branch workflow Advantages: I master always consistent and (hopefully) working, I less merges while concurrent development, I easier to manage, I interesting commit tree. :-) Merging: I open merge request, I have somebody review changes, I ideally review and test code before accepting merge. Feature branch workflow Feature branch workflow General idea: I features get developed in individual branches, I when ready: merge into master branch, 14 – Francis Colas – git basics Merging: I open merge request, I have somebody review changes, I ideally review and test code before accepting merge. Feature branch workflow Feature branch workflow General idea: I features get developed in individual branches, I when ready: merge into master branch, Advantages: I master always consistent and (hopefully) working, I less merges while concurrent development, I easier to manage, I interesting commit tree. :-) 14 – Francis Colas – git basics Feature branch workflow Feature branch workflow General idea: I features get developed in individual branches, I when ready: merge into master branch, Advantages: I master always consistent and (hopefully) working, I less merges while concurrent development, I easier to manage, I interesting commit tree. :-) Merging: I open merge request, I have somebody review changes, I ideally review and test code before accepting merge. 14 – Francis Colas – git basics Feature branch workflow Practically In practice: I git checkout -b new_feature I code, test, code more, test even more... I git status I git add <files> I git status I git commit -m "new feature" I git pull I git push -u origin new_feature I merge request I get it accepted I git checkout master I git pull I git branch -d new_feature I git remote prune origin 15 – Francis Colas – git basics Feature branch workflow Merge request From the command line: I git stash I git checkout master I git checkout -b merging_new_feature I git fetch I git merge new_feature I code review I test (compilation, unit tests, etc.) I git checkout master I git merge new_feature I git push I git checkout your_branch I git stash pop 16 – Francis Colas – git basics 05 Conclusion Conclusion Conclusion git: I not complex to use, I good for one or many people, I good for connected or offline work; Feature branch model: I convenient in big projects, I state-of-the-art use of git. 18 – Francis Colas – git basics + Thanks for your attention. 18 – Francis Colas – git basics.