GIT: a Gentle InTroduction
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The document is an introduction to Git, a distributed version control system, covering its fundamental concepts such as local operations, branching, and merging. It emphasizes the integrity and local nature of Git with its snapshots and internal object database, along with differences from traditional centralized systems. Additionally, it addresses enterprise adoption challenges and solutions for using Git in organizational environments.
GIT: a Gentle InTroduction
- 1. GIT: (a) Gentle InTroduction! Bruno Bossola
- 2. Agenda About version control
- 3. Concepts
- 7. Q&A
- 8. Hey dude who are ya?? Developer since 1988
- 9. XP Coach during 2k
- 10. Co-founder and coordinator of JUG Torino
- 11. Java Champion since 2005
- 13. Working as contractor across Europe
- 14. About version control Picture courtesy of globalnerdy.com All rights kindly reserved
- 16. SVN Picture courtesy of progit.org. All rights kindly reserved
- 18. Mercurial
- 19. Bazaar Picture courtesy of progit.org. All rights kindly reserved
- 20. Concepts
- 21. Concepts Snapshots, not deltas
- 22. Nearly every operation is local
- 23. Integrity is a priority
- 25. Snapshot, not deltas Deltas are maintained: CVS, SVN, Bazaar Picture courtesy of progit.org. All rights kindly reserved
- 26. Snapshot, not deltas Full file is maintained: Git , BitKeeper Picture courtesy of progit.org. All rights kindly reserved
- 27. Most operations are local Your local database contains a full copy of the remote(s)
- 28. Browsing, changing, search happens locally
- 29. Almost everything doable without network
- 30. the db is a nice, separate .git folder :)
- 31. Integrity is a priority Everything in Git is check-summed SHA-1 hash
- 32. 40-character string such as 95b87297210672b16bb70ded20626c9c551ccd58 It's impossible to make a change without Git knowing it!
- 33. Git generally only adds data
- 34. The three states modified
- 35. staged
- 36. committed
- 37. all local operations! Picture courtesy of progit.org. All rights kindly reserved
- 39. Initializing a local repository
- 40. Managing files
- 42. Local operations
- 43. How does it work Git has an internal object database
- 44. It contains blob (files)
- 45. commit
- 46. tree
- 47. …and other stuff :)
- 48. After a commit... Picture courtesy of progit.org. All rights kindly reserved
- 49. After three commits... Picture courtesy of progit.org. All rights kindly reserved
- 50. A branch is a pointer Picture courtesy of progit.org. All rights kindly reserved
- 51. Creating a branch Picture courtesy of progit.org. All rights kindly reserved > git branch testing
- 52. HEAD HEAD: a special pointer so Git knows where you are Picture courtesy of progit.org. All rights kindly reserved
- 53. Switching to a branch Git moves HEAD pointer to the branch pointer Picture courtesy of progit.org. All rights kindly reserved > git checkout testing Switched to branch 'testing'
- 54. Change a file (on a branch) Git keeps following with HEAD the branch pointer Picture courtesy of progit.org. All rights kindly reserved > vi readme.txt > git commit -a -m 'readme file updated'
- 55. Switch to master Git moves back HEAD to point to master Picture courtesy of progit.org. All rights kindly reserved > git checkout master
- 56. And change again! Git still keeping separate pointers to the branches Picture courtesy of progit.org. All rights kindly reserved > vi readme.txt > git commit -a -m 'readme file now rocks!'
- 57. Time to merge! A new “merge” commit is generated Picture courtesy of progit.org. All rights kindly reserved > git merge testing Merge made by recursive. 1 files changed, 1 instions(+), 0 dltions(-)
- 59. What's a remote? You can have multiple remote repos usually one, “origin”
- 60. sometimes one main r/w, other r/o,
- 61. rarely multiple Collaborating means pushing and pulling data from the remote repos
- 62. Using a remote: clone Move into an empty folder... Different protocols are available git (native)
- 63. http(s)
- 64. ssh You get a full copy of the repository > git clone <url>
- 65. (less usual) Add a remote Move into an existing git folder...
- 66. Mostly used when working with multiple repositories > git remote add <name> <url>
- 67. Initial clone Picture courtesy of progit.org. All rights kindly reserved
- 68. How do it syncs? “master” is tracked automatically
- 69. “fetch” command will download all the updates from the remote db “merge” to merge the branches
- 70. “rebase” (let's see this later) “pull” is a shortcut for fetch + merge
- 71. I do some work... Picture courtesy of progit.org. All rights kindly reserved
- 72. Someone else pushes! Picture courtesy of progit.org. All rights kindly reserved
- 73. Synchronize with fetch Picture courtesy of progit.org. All rights kindly reserved
- 74. What next? Fetch is just fetching all the data, nothing changes
- 75. To update your master copy to the remote you may: Merge
- 76. Rebase You can have done a pull (fetch + merge)
- 77. Merge! Git uses an automatic three-ways merge algorithm very efficient :)
- 78. Most of the time it's a piece of cake
- 79. Any conflict not resolved automarically must be resolved... by you (as usual!)
- 80. Rebase! First removes from the target branch the diverging commits
- 81. Then adds all the changes committed on the source other branch
- 82. Then adds your commits on top
- 83. Rebase! After a rebase,,, Picture courtesy of progit.org. All rights kindly reserved
- 84. Rebase! No differences in result
- 86. Branches are then easy to integrate to the master
- 87. Quick demo! Cloning a repo
- 88. Fetching from a remote
- 91. Issues in the enterprise? No security out of the box secure protocols are based on OS services
- 92. no way to restrict the access to a repository
- 93. no way to lock a branch
- 94. no audit
- 95. you can commit in behalf of someone else
- 96. More issues in the enterprise! No easy setup for users and groups
- 97. administration is a pain (again based on the OS services)
- 98. Only basic repository visualization (and nothing on the remote)
- 99. Solutions? use a predefined solution on top of a *nix environment gitolite
- 100. gitosis get an industrialized service gitenterprise (yeah, the plug, finally!)
- 101. github-fi
- 102. …not much more here :)
- 103. Questions?
- 104. Thanks!