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Introduction to git administration

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Short set of slides, brief intro to Git then shared experiences migrating from other SCM tools to Git.

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Introduction to git administration

  1. 1. Introduction to Git Administration For New Administrators Shawn Doyle ReleaseTEAM Inc sdoyle@releaseteam.com www.linkedin.com/in/releaseteam/ http://twitter.com/ReleaseTEAMInc
  2. 2. Premium SCM Consulting firm since 1999 Focus on Software Configuration Management On site and remote consulting services – Build Automation – CM tool administration, customization, upgrades, migrations Classroom training / hands-on mentoring R e l e a s e T E ClearCase ClearQuest Jenkins Git RTC Build Forge SVN Jira Electric Commander Shawn Doyle - ReleaseTEAM
  3. 3.  For the administrator new to Git  An overview of Git  Workflows  Common admin tasks  Access control  Triggers  Stories from the trenches Subversion & Git Presentation Agenda Slide 4
  4. 4. So you now are a Git Admin
  5. 5. Git has sprung up in many organizations. Spreading like a wild fire from the development groups. – Developers want less restrictions to their productivity – SCM is always seen as a restriction and rarely a necessary one SCM admins are finding they need to support Git regardless of existing corporate standards. SCM admins need to find a way to control the chaos. Most commercial SCM tools now support Git as a client. Don’t panic Git is fun, powerful and it is the future. Subversion & Git Presentation Wait.. What? how did this happen Slide 6
  6. 6. DVCS – Learn the difference Users – Training – Indulging the Git promoter(s) Many solutions to common problems – Authentication – Workflows – Multiple available UIs Cleaning up after user mistakes Subversion & Git Presentation What am I in for? Slide 7
  7. 7. 1. RTFM http://git-scm.com/book 2. Now that you read the Git book, go thru these tutorials 3. Watch these videos - Google Tech Talks Linus Torvalds on git Randal Schwartz on Git 4. RTFW https://git.wiki.kernel.org/index.php/Main_Page 5. Create a repo and start playing! Subversion & Git Presentation How I learned Git Slide 8
  8. 8. Tutorials http://try.github.io/levels/1/challenges/1 Code School https://www.atlassian.com/git/tutorial/git-basics Atlassian's Git tutorial http://gitready.com/ Git Ready https://www.kernel.org/pub/software/scm/git/docs/everyday.html Everyday GIT With 20 Commands Or So Videos - Google Tech Talks http://www.youtube.com/watch?v=4XpnKHJAok8 Linus Torvalds http://www.youtube.com/watch?v=8dhZ9BXQgc4 Randal Schwartz Wiki https://git.wiki.kernel.org/index.php/GitCommunity|Git Community Wiki Subversion & Git Presentation Resources Slide 9
  9. 9. Git Overview Subversion & Git Presentation Slide 10
  10. 10. When coming from another SCM system to Git you need to shift how you think about how version control works. In a more classic SCM you think of it as a system that versions files in a tree or directory structure. Git is better thought of as a system that versions trees of files. Biggest Obstacle
  11. 11. Stores whole copies of the repo – No file deltas – Entire tree is captured at each commit not just the files that changed, a snapshot of the repo Branches and tags – Are pointers to commits – Very fast and light weight Subversion & Git Presentation How Git Works Slide 12
  12. 12. Git is: – Powerful – Complex – Fast (local) – worthy contender to replace many commercial tools – the solution you are looking for Object Storage – Blobs – SHA1s or hashes – Trees Perl like syntax – ^ $ ~ … Subversion & Git Presentation Not Scared yet? Slide 13
  13. 13. Workflows
  14. 14. Centralized – Central repository Feature Branch – Central repository + branching per features Gitflow – Branches per features, releases and bug fixes Forking – Distributed workflow Workflows
  15. 15. Uses a central repository – single point-of-entry for all changes – Everyone clones from the central repo – Everyone pull/pushes from the same repo Benefits – SCM Admin can put controls/triggers on the central repo – Security can be setup using tools like • Stash • Gitolite • Gitosis – SCM Builds and Deploys can be maintained from a clone of the central repo. Centralized
  16. 16. Development of features in isolated branches – Allows features to be developed independently As a feature is finished it is merged to the master branch Subversion & Git Presentation Feature Branch Slide 17
  17. 17. Branches are focused around releases Branches are also used for – Release – Integration or Test – Features Strict rules on how and when branches interact Subversion & Git Presentation Gitflow Slide 18
  18. 18. Repos are forked per developer – Developers work in isolation One Repo is declared as the Official Repo – A Project Maintainer integrates the Repos – Developers sync with the Official Repo Subversion & Git Presentation Forking Slide 19
  19. 19. Common Admin Tasks
  20. 20. What to Migrate? Snapshot in time or all history? – Push for converting a snapshot in time – If that fails, then try for a few key slices – Arguments • Why burden the new repo with all the history • Populating new workspaces will take longer • Leave old SCM system in a locked down state for reference – Refactoring • Always a good time to refactor when switching SCM system • Can cause headaches if under deadlines – Builds • How dependent were you on the old SCM for builds – Paths – Build tools (e.g. clearmake) – APIs, Libs Migration Considerations
  21. 21. Client and Server concepts Use a Client side hook for actions – Commit – Merge – Rebase Server Hooks – Notification – Rejecting Pushes Hooks need to be copied to the repos – Hooks are not part of cloning – Hooks do not get updated with pull/pushes In general, use hooks in Git to encourage workflow or for notifications. Do not rely on them to enforce security Subversion & Git Presentation Hooks Slide 22
  22. 22. Be Clever – There is no one way to provide Security – There is no single definition of Security SSH keys Git Repository Management – Stash – Gitolite – Github Triggers Subversion & Git Presentation Security Slide 23
  23. 23. Sometimes a user removed something they didn’t mean to. The following commands are your friends when trying to figure out what to restore and from where. – Git log – Git relog – Git reset – Git update-ref Repos for backups – Create clones on a safe network disk – Pull to them once a day (or once a week) – Use them to recover files or as a reference Subversion & Git Presentation Recovering files Slide 24
  24. 24. Stories from the trenches
  25. 25. Builds failed after migrating a project from ClearCase to Git – Dev group certain the migration to Git had failed – Build depended on a large number of sub directories to exist – Git does not add empty directories • It needs a blob to point to a directory for the directory to exist. – Solution was to initially add the missing directories • Created .temp files in each empty dir • This creates a blob and the directory is added to Git – Long term solution • Encourage them to fix their build Ant/Make files. Empty Directories
  26. 26. A user added multiple large files to his repo – Then committed them and pushed them to the central repo User removed them with ‘git rm –rf’ Why is this bad? – Clone commands went from seconds to 20 minutes Why? – Git didn’t remove the large files from the initial commit – Clone copies the entire repo locally, those files while no longer visible are still copied Solution – Git filter-branch – Git gc – Git prune Subversion & Git Presentation Slow Clones Slide 27
  27. 27. Client Requirements – Contractors limited to sub dirs. – All files in a single Repo. Git by design – Does not preserve directory permissions – Hooks run before or after a Git command – Submodules don’t offer additional protections • Also broke the client single repo requirement Subversion & Git Presentation Directory Isolation Slide 28
  28. 28. Client workflow depended on Tags Git Tags are not shared by default – Tags need to be explicitly; • Pushed to the remote • Pulled locally Solutions – Reevaluate Workflow – Share pull command with Tag name – Share Hash Subversion & Git Presentation Universal Tags Slide 29
  29. 29. Client wanted to control who could create a local repo – Git is not designed to do this You can limit who can clone from a central Repo – Stash/Gitolite – SSH Keys Once a Repo is cloned – Nothing is stopping the user from cloning it again – They can allow others to clone Solution – Lock down who can push back to the central Repo Subversion & Git Presentation Controlling local repos Slide 30
  30. 30. Client wants to Clone one subdir of a Repo – Build requires entire Repo – Deploy requires one sub dir – Build happens weeks before the deploy – Deploy wants a fresh Repo • Just build results and deployment script Solution – Submodules Subversion & Git Presentation Partial Clone Slide 31
  31. 31. Questions Shawn Doyle ReleaseTEAM Inc sdoyle@releaseteam.com www.linkedin.com/in/releaseteam/ http://twitter.com/ReleaseTEAMInc

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