Git slides
- 1. git you won't learn git in twenty minutes at a LUG but here are twenty-odd slides anyway sorry there are no pictures David Spencer Bradford Linux Users Group 14 September 2015
- 2. quick quiz Who uses it? or has tried it? or wants to try it, started reading about it, and got put off? What do we know about it? ● purpose ● history ● other similar tools (has anybody here used other tools?)
- 3. what source code control system revolutionised a stale technology popular, or even trendy (this was not foreseeable) Github is the new Sourceforge... Github is the new Linkedin? Github is the new Blogger? Github is the new git?
- 4. who and why and when January 2002: Linus doesn't scale Bitkeeper trial the only suitable software, but proprietary Early 2005: terminated amicably but suddenly Tridge reverse engineered the Bitkeeper protocol 2.6.12-rc2 left high and dry Linus coding binge
- 5. I'm an egotistical bastard, and I name all my projects after myself. First 'Linux', now 'Git' 3 April 2005 - started 6 April - announced 7 April - self hosting 11 April - "I don't even know yet. I'm playing around with my own scripts and tools right now" 18 April - first big Linux merge 29 April - merging Linux at 6.7 patches/sec 16 June - 2.6.12 released 26 July - Linus hands over to Junio Hamano 21 December - git-1.0
- 6. design Fast Distributed data store, and distributed workflow Scales well CVS as an example of what not to do (if in doubt, do the opposite) Really just a name/value data store (colossal understatement) Strong safeguards against corruption
- 7. what's it useful for? why should we care? Answering the second question first: because lots of other people find it useful Answering the first question second: working with other people (and maybe keeping your own stuff tidy)
- 8. Use The Source Command line git clone http://github.com/darktable-org/darktable.git network aware receive a subdirectory 'darktable' contains (a) the source tree (as if you'd extracted a tarball) (b) hidden directory .git/ with ALL the metadata bang up to date just follow the instructions like a tarball
- 9. Contribute back Your 'git clone' is a first class copy You can modify it and offer the changes back ("pull request", or send email patches) You can push the changes back if authorised git push You can distribute independently (fork) You can receive and merge changes (from "upstream" ... from anywhere) git fetch, git merge, git pull
- 10. How it works Initialise a new directory or existing directory tree or clone .git contains a key-value store Keys are SHA-1 40 character hex hashes Values are file deltas (1) highly efficient to store and restore (2) cryptographically secure That doesn't sound like CVS or Visual Studio! ... until you realise ... (3) file deltas == file history
- 11. How it works Source management commands ("porcelain") are implemented as key/value store operations ("plumbing") edit edit edit edit Looks good? git add <filenames> hm, maybe a bit more editing git add <filenames> don't need that any more git rm <filename> Yes that's good git commit -m 'Description of my changes'
- 12. commits identified by 40 character hex string (old systems just used increasing revision number) but can be truncated to just first few (7-ish) aliases: HEAD, tag (release), branchname (just identify a key in the key-value store) you can go back to a commit, diff with a commit, read the message, cherry-pick, format a patch...
- 13. branches Ever had some script that worked well but you wanted to make some improvements stuffed it up wished you could go back? or even have two versions one stable the other experimental? This is what branches are for
- 14. branches Ever had multiple people working on different aspects of the same project? Falling over each other's incompatible changes? This also is what branches are for Merging them is tricky git has lots of handy solutions for that git diff, three way diff tools (meld) git merge, git rebase
- 15. history Who made these changes and when? git log git blame It used to work, what change introduced this bug? git bisect
- 16. history cryptographically secure => history cannot be falsified => can be rewritten (quick quiz) => anyone with old history will experience pain (quick quiz) Once you publish your commits don't rewrite history not ever ... srsly git commit --amend
- 17. Github Uses: Sourceforge without the smell of death and client-side too Abuses? blogs, articles Controversies China, DMCA Alternatives Atlassian Bitbucket https://bitbucket.org/
- 19. crappiness git extensions (mostly crap) git graphical interfaces (mostly crap) Not crap: github, cgit merge conflicts in the middle of a rebase JUST FORGET THAT CRAP DAMN YOU <RAGEFACE> crappy people who don't do releases Learn how to use git tag, srsly projects still using other crap svn mercurial bzr ... people who tell people they are doing git wrong gitflow == follow my crap rules, you'll feel secure and I'll feel important
- 20. learning Vast amount of tutorials, mostly crap Annoying diagrams of commits and branches Annoying terminology (index, staging) Command line inconsistencies Git manpages ok-ish Github help is crap Learn by doing (doesn't work for scary stuff) https://try.github.io/levels/1/challenges/1
- 21. learning Worked tutorials https://try.github.io/ http://rogerdudler.github.io/git-guide/ Pro Git (book) https://git-scm.com/book/en/v2 Git from the bottom up http://ftp.newartisans.com/pub/git.from.bottom.up.pdf Manpages https://git-scm.com/docs and man git-thing https://training.github.com/kit/downloads/github-git-cheat-sheet.pdf So you have a mess on your hands http://justinhileman.info/article/git-pretty/git-pretty.pdf
- 22. learning Linus on YouTube (2007, long) https://www.youtube.com/watch?v=4XpnKHJAok8 Linus on YouTube (2009, even longer) https://www.youtube.com/watch?v=8ET_gl1qAZ0 Adolf on YouTube (1945, very short) https://www.youtube.com/watch?v=CDeG4S-mJts
- 23. some new words we learned today repository commit, history branch, fork, clone, tag HEAD master index, working tree fetch, merge, pull, push patch