Git Agility

An advanced ~3 hour git workshop that premiered in Turku Agile Day 2012

Transcript

1. Git Agility
2. whoami
3. Software engineer @ Spotify Jyrki Pulliainen
4. @nailor
5. Hottest hot in 2006! Using git since v1.3.0
6. git clone git://github.com/nailor/git-training.git Clone the repo!
7. Data representation
8. $ tree . ├── module │ ├── __init__.py │ └── main.py ├── README └── setup.py 1 directory, 4 files
9. commit tree blob master HEAD
10. $ git symbolic-ref HEAD refs/heads/master $ git rev-parse refs/heads/master 533276ca932fd605644eddd2a08d5c556736c278 $ git cat-file -p 533276ca tree 8f7bc7153c59949e10822512a9ceb07d470bd9ff parent a5c2044e43c5415330d26db1dd74e0b897b7179b author Jyrki Pulliainen <jyrki@spotify.com> 1336331027 +0200 committer Jyrki Pulliainen <jyrki@spotify.com> 1336331027 +0200 Remove reference to common.py
11. COMMIT size tree 34ff parent 0d54 author jyrki committer jyrki some nice commit msg TREE size blob 14ff README blob fd21 setup.py tree dd98 module TREE size blob 9eab __init__.py blob cafe main.py BLOB size #!/usr/bin/python setup(...) BLOB size def main(...) BLOB size # Copyright supercorp b3cf 34ff fd21 dd98 9eab cafe
12. Three trees HEAD, the index and the working directory
13. "What's in the repository" HEAD
14. "What's going in to the repository" The index
15. $ git status # On branch master # Changes to be committed: # (use "git reset HEAD <file>..." to unstage) # # modified: README # What's the difference between index and HEAD
16. The working directory
17. $ tree . ├── module │ ├── __init__.py │ └── main.py ├── README └── setup.py 1 directory, 4 files
18. $ git status # On branch master # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: README # no changes added to commit (use "git add" and/or "git commit -a") What's the difference between index and working directory
19. Moving between trees
20. HEAD INDEX WORKING DIRECTORY Stage files Do a commit Check out a branch / Clone project
21. Working with trees
22. HEAD INDEX WORKING DIRECTORY git add git commit git checkout
23. add vs reset
24. File v. 1 HEAD INDEX WORKING DIRECTORY git add File v. 2 File v. 2 File v. 1 File v. 1 git reset
25. checkout
26. HEAD INDEX WORKING DIRECTORY File v. 1 File v. 2 File v. 2 File v. 1 git checkout File v. 1 File v. 1
27. reset --hard, --mixed --soft
28. hard mixed [the default] soft Move the HEAD back, reset the index but leave working directory Move the HEAD back and reset the working directory Move the HEAD back
29. git reset --soft HEAD~2; git commit squash two previous commits together
30. Tutorial Edit a file in working directory and add it to index. Reset index, re-add and do hard reset. Edit the file again and commit this time. Do a soft reset and commit Try git checkout HEAD^ -- file
31. Two categories of commands Plumbing Porcelain http://www.flickr.com/photos/notionscapital/2948697649/
32. Porcelain git add git commit git pull git fetch git merge git status .... Plumbing git apply git commit-tree git pack-objects git update-ref git write-tree git merge-index ...
33. Referencing git objects protip: git help revisions
34. • <shaid>, eg. 'deadb33f' • <revname>, eg. 'v1.0' • <ref>, eg. 'master', 'origin/master' • <refname>@{<date>}, eg. master@{1 year ago} • <refname>@{<n>}, eg. master@{4} • <rev>^, eg. HEAD^ • <rev>~[n], eg. HEAD~5
35. A B C D E master master^2 master^ master~2
36. $ git show :/fix # Show latest commit containing "fix" $ git show :/^Merge # Show latest merge commit
37. $ git show v1.0^{commit} # Show commit object related to tag v1.0 $ git show HEAD^{tree} # Show a tree that contains the full history Funny stuff, don't try at hom e
38. Tutorial Find the last commit that talks about snakes Find the second parent of commit referenced by branch terrario
39. Everyday helpers
40. Short status
41. $ git status # On branch master # Changes to be committed: # (use "git reset HEAD <file>..." to unstage) # # new file: snakepit/__init__.py # # Untracked files: # (use "git add <file>..." to include in what will be committed) # # snakepit/reptile.py
42. $ git status -sb ## master A snakepit/__init__.py ?? snakepit/reptile.py
43. Word diffing
44. $ git diff diff --git i/README w/README index bae3a1d..779cc2a 100644 --- i/README +++ w/README @@ -3,4 +3,4 @@ Please read this. However, ignore this line, as this talks about something you don't really gain anything by reading it. -And you know, mice are the coolest animals in the world. +And you know, honey badgers are the coolest animals in the world. Do removals, modifications and untracked files. Compare output of status and short status. Add something in the index, see how diff --cached works
45. $ git diff --word-diff diff --git i/README w/README index bae3a1d..779cc2a 100644 --- i/README +++ w/README @@ -3,4 +3,4 @@ Please read this. However, ignore this line, as this talks about something you don't really gain anything by reading it. And you know, [-mice-]{+honey badgers+} are the coolest animals in the world.
46. git log --decorate --oneline --graph
47. $ git log --graph --oneline --decorate * 57d3792 (HEAD, master) Merge branch 'reptiles' |\ | * fc78165 (reptiles) Declare reptiles! * | 46592b0 Change mice to honey badgers * | 19d7900 Expand README |/ * 514a1ad Add snakepit module * 9ab964b Initial commit
48. What am I committing?!? git diff --staged
49. $ git status -sb ## master M snakepit/reptile.py $ git diff --staged # some boilerplate removed +++ i/snakepit/reptile.py @@ -2,3 +2,7 @@ def is_reptile(reptile): if reptile is 'worm': return False return True + + +def snakes(): + return ['viper', 'python', 'boa']
50. Tutorial Do removals, modifications and untracked files. Compare output of status and short status. Add something in the index, see how diff -- staged works
51. Patch interface
52. git add --patch git reset --patch git checkout --patch
53. Tutorial Add text to README. Use add -p to add it in to the index. Try patch reset to revert it, but use edit command for it, and try reverting it. Reset working dir with git checkout -p
54. Merging
55. What happens in a merge?
56. A B C D E my-branch master Fast-forw ard m erge master
57. A B C D E my-branch master True m erge master F HEAD MERGE_HEAD HEAD
58. Branches
59. $ git branch -a conflict * master reptiles remotes/origin/master remotes/origin/conflict
60. $ git branch foo [ref] # Create a new branch foo at ref $ git checkout -b foo [ref] # Create a new branch foo at ref and switch to it $ git branch -d foo # Delete branch foo
61. $ git branch -a * master remotes/origin/master remotes/origin/conflict
62. $ git checkout conflict # Create branch conflict at origin/conflict and set up # tracking $ git checkout -b conflict origin/conflict # Same as above $ git checkout -t conflict # Same as above $ git checkout -b conflict # Just create a local branch called conflict
63. $ git push origin master # Push branch master to origin and create it, if it does # not exist $ git push origin master:new-master # Push master to remote branch new-master $ git push origin :master # Delete remote branch master $ git push origin +master # Force push master to origin overwriting the remote # information about master branch
64. $ git push -u origin master # Push branch master to origin and create it, if it does # not exist. Set up tracking for the branch.
65. $ git config --global push.default [value] # From man page: # nothing - do not push anything. # matching - push all matching branches. All branches # having the same name in both ends are considered to # be matching. This is the default. # upstream - push the current branch to its upstream # branch. # tracking - deprecated synonym for upstream. # current - push the current branch to a branch of the # same name.
66. Merge conflict resolution
67. $ git diff diff --cc INSTRUCTIONS index 63c473b,8cf737a..0000000 --- i/INSTRUCTIONS +++ w/INSTRUCTIONS @@@ -1,1 -1,1 +1,5 @@@ ++<<<<<<< HEAD +There are important ones ++======= + There is none! ++>>>>>>> conflict
68. $ git show :1:INSTRUCTIONS # the common ancestor $ git show :2:INSTRUCTIONS # the HEAD version (our) $ git show :3:INSTRUCTIONS # the MERGE_HEAD version (theirs)
69. $ git checkout --ours INSTRUCTIONS # Check out our (HEAD) version of file $ git checkout --theirs INSTRUCTIONS # Their version of the file (MERGE_HEAD) $ git checkout -m INSTRUCTIONS # Check out the merge conflict version
70. $ git log --merge # What commits touched these files?
71. Actual fixing
72. $ git diff diff --cc INSTRUCTIONS index 63c473b,8cf737a..0000000 --- i/INSTRUCTIONS +++ w/INSTRUCTIONS @@@ -1,1 -1,1 +1,1 @@@ - There are important ones -There is none! ++There are important nones!
73. $ git add [file] # This is done, mark it as merged $ git reset --hard # reset the whole merge conflict
74. $ git checkout --conflict=diff3 [file] # Create a three way diff with the common # base of the file
75. $ git checkout --conflict=diff3 INSTRUCTIONS $ git diff diff --cc INSTRUCTIONS index 63c473b,8cf737a..0000000 --- i/INSTRUCTIONS +++ w/INSTRUCTIONS @@@ -1,1 -1,1 +1,7 @@@ ++<<<<<<< ours +There are important ones ++||||||| base ++There are some ++======= + There is none! ++>>>>>>> theirs
76. Merge tools
77. $ git config merge.tool "tool" # valid values "araxis", "bc3", "diffuse", "ecmerge", # "emerge", "gvimdiff", "kdiff3","meld", "opendiff", # "p4merge", "tkdiff", "tortoisemerge", "vimdiff" and # "xxdiff" $ git mergetool
78. Tutorial Merge branch conflict to master. View diff with git diff Investigate with git log --merge Try checking out different versions of file and reset with git checkout -m Try git checkout --conflict=diff3 Solve the merge
79. Reuse Recorded Resolution
80. $ git config --global rerere.enabled 1 $ git config --global rerere.autoupdate 1 # Not really necessary, as we'll see soon
81. Avoid solving same stuff again ...and again and again...
82. $ git merge conflict $ git rerere status # Solve merge conflict $ git add [file] $ git rerere diff $ git commit
83. $ git merge conflict Auto-merging snakepit/reptile.py CONFLICT (add/add): Merge conflict in snakepit/reptile. py Auto-merging INSTRUCTIONS CONFLICT (add/add): Merge conflict in INSTRUCTIONS Resolved 'INSTRUCTIONS' using previous resolution. Resolved 'snakepit/reptile.py' using previous resolution.
84. Tutorial Merge branch conflict-other to master. Use rerere to record resolution. Resolve conflict and commit. Reset master to state before merge. Check out conflict-other and rebase it on master.
85. History rewriting
86. $ git commit --amend
87. $ git reset --soft HEAD~5 && git commit
88. git cherry-pick
89. $ git cherry-pick D
90. A B C D E my-branch master D' master
91. git rebase Swiss army tool of history editing
92. $ git rebase master
93. A B C D E my-branch master D' E' my-branch
94. $ git rebase server --onto master
95. A B C D E my-branch master D' E' my-branch H server
96. git rebase -i
97. pick ab8f5ff Add some instructions pick d8c062e Add newline pick 8e10e9b There are some important instructions # Rebase e9a922e..8e10e9b onto e9a922e # # Commands: # p, pick = use commit # r, reword = use commit, but edit the commit message # e, edit = use commit, but stop for amending # s, squash = use commit, but meld into previous commit # f, fixup = like "squash", but discard this commit's log message # x, exec = run command (the rest of the line) using shell # # If you remove a line here THAT COMMIT WILL BE LOST. # However, if you remove everything, the rebase will be aborted. #
98. Tutorial Switch honeybadger and "Add snake" master. Rename "Add snake" to "Add viper". Rebase conflict on top of master. If you have rerere, what happened?
99. Aborting
100. git reflog
101. $ git reflog 250ed94 HEAD@{0}: checkout: moving from master to terrario 250cfb0 HEAD@{1}: checkout: moving from terrario to master 250ed94 HEAD@{2}: checkout: moving from master to terrario 250cfb0 HEAD@{3}: commit: Add line to README. ad11e8c HEAD@{4}: reset: moving to HEAD~ b387bb7 HEAD@{5}: commit: Add line to README ad11e8c HEAD@{6}: clone: from git@github.com: nailor/git-training.git
102. Stashing
103. Save the state of your workdir
104. $ git status -sb ## master M snakepit/reptile.py $ git stash save 'def for later' Saved working directory and index state On master: def for later HEAD is now at ad11e8c Honeybadger here. $ git stash list stash@{0}: On master: def for later $ git stash show stash@{0} snakepit/reptile.py | 4 ++++ 1 file changed, 4 insertions(+)
105. $ git stash [save] $ git stash --keep-index $ git stash --patch # git stash -p $ git stash --include-untracked # git stash -u
106. $ git stash apply $ git stash pop $ git stash drop $ git stash branch <branchname>
107. Bisecting The bugs, where do they all come from?!?!
108. $ git bisect start $ git bisect good [committish] $ git bisect bad [committish]
109. Tutorial Start bisect and mark 9ab964b9 as good and master as bad. Find commit that introduces honey badgers.
110. Easing out
111. Aliases
112. $ git config --global alias.lokg \ --graph --abbrev-commit --pretty=oneline --decorate $ git config --global alias.unmerged \ '!f() { git ls-files --unmerged | cut -f2 | sort -u ; }; $EDITOR `f`' $ git config --global alias.add_unmerged \ '!f() { git ls-files --unmerged | cut -f2 | sort -u ; }; git add `f`'
113. Detached head (just for giggles)
114. $ echo "Detached history" | \ git commit-tree master~^{tree} $ git branch history <commit>
115. B history A C D master history
116. $ git cherry-pick master $ git replace badbeef master~
117. B history A C D master history D'
119. Reasons? • Switching from one SCM to another • Cleanup (meh)
120. git clean
121. $ git clean -f # Actually do something $ git clean -x # Remove files in gitignore $ git clean -d # Remove untracked directories $ git clean -X # Remove only files ignored by git
122. Questions?
123. Thank you!