Advanced Git Techniques: Subtrees, Grafting, and Other Fun Stuff
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The document discusses advanced Git techniques, including the use of git subtree for managing sub-projects and external libraries. It covers commands for injecting projects, extracting folders, and interactive staging to customize commit history. Additionally, it highlights scenarios where git subtree is beneficial and alternatives for handling complex dependencies.
![Aliases to make your life easier!
[alias]
sba = "!f() { git subtree add --prefix $2 $1 master --squash; }; f"
sbu = "!f() { git subtree pull --prefix $2 $1 master --squash; }; f"
Alias section of your .gitconfig
http://bit.do/git-aliases](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-12-320.jpg)
![We modify a single file in 3 different parts
[:~/p/demo] master(+3/-0) ± git diff
@@ -1,11 +1,14 @@
# Title
Content of my article
+Adding a second line to Title.
## Subtitle second heading
Some more paragraph content
+Adding another line to Subtitle 1
## Conclusions
Here are your conclusions](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-23-320.jpg)
![Overview of
interactive
staging [2]
add untracked
Check the unstaged or staged
changes in the workspace.
patch
Add parts of a file to the staging area.
This allows you to split commits.
diff
Add new untracked files to the
repository.](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-26-320.jpg)
![If the default hunk size is too big, you can split it:
Stage this hunk [y,n,q,a,d,/,s,e,?]? s
Split into 3 hunks.
@@ -1,7 +1,8 @@
# Title
Content of my article
+Adding a second line to Title.
## Subtitle second heading
Some more paragraph content](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-32-320.jpg)
![Let’s stage this hunk, or add it to the staging area:
Stage this hunk [y,n,q,a,d,/,j,J,g,e,?]? y
@@ -4,8 +5,9 @@
## Subtitle second heading
Some more paragraph content
+Adding another line to Subtitle 1
## Conclusions
Here are your conclusions
Stage this hunk [y,n,q,a,d,/,K,j,J,g,e,?]?](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-33-320.jpg)
![The result is a neat new commit and the rest left:
14a0be4 [4 minutes ago] (HEAD -> master) Add content to Title [Nick]
git diff
diff --git i/README.md w/README.md
index fc26295..0ef85c4 100644
--- i/README.md
+++ w/README.md
@@ -6,7 +6,9 @@ Adding a second line to Title.
## Subtitle second heading
Some more paragraph content
+Adding another line to Subtitle 1
## Conclusions](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-35-320.jpg)
![When you need help just press “?”
Stage this hunk [y,n,q,a,d,/,s,e,?]? ?
y - stage this hunk
n - do not stage this hunk
q - quit; do not stage this hunk or any of the remaining ones
a - stage this hunk and all later hunks in the file
d - do not stage this hunk or any later hunks in the file
g - select a hunk to go to
/ - search for a hunk matching the given regex
j - leave this hunk undecided, see next undecided hunk
J - leave this hunk undecided, see next hunk
k - leave this hunk undecided, see previous undecided hunk
K - leave this hunk undecided, see previous hunk
s - split the current hunk into smaller hunks
e - manually edit the current hunk](https://image.slidesharecdn.com/build-09-paolucci-151102172750-lva1-app6891/85/Advanced-Git-Techniques-Subtrees-Grafting-and-Other-Fun-Stuff-36-320.jpg)
Advanced Git Techniques: Subtrees, Grafting, and Other Fun Stuff
- 1. NICOLA PAOLUCCI • DEVELOPER INSTIGATOR • ATLASSIAN • @DURDN Advanced Git Techniques Subtrees, grafting and other fun
- 2. Get more out of your version control.
- 3. Today we’ll cover some powerful Git goodies Interactive stagingPainless sub-projects Collating history Interactive commits are an amazing tool at your disposal as you work on complex code changes You can use git subtree to handle external libraries in a clean and efficient way Joining together history of your projects using git replace is useful when migrating to Git
- 4. git subtree Extract project Alternative to git submodule to handle external dependencies. Inject dependency It allows you to inject an external project into a sub-folder Introduced in 1.7.11 It can be also used to extract a sub-folder as separate project
- 5. Clean integration pointsStores in regular commitsNo training When and why is git subtree a great choice Does not require your entire team to be trained in the use of the command The command stores the external dependency in regular Git commits. Squashing the history optionally. It makes it easy to see when integrations happened and makes it easy to revert them.
- 6. Syntax to inject a project Command to inject project git subtree add --prefix target-folder https://bitbucket.org/team/sub.git master --squash Folder where to insert code Repository URL v1.1
- 7. Under the hood of git subtree commit ab54c4e0b75c3107e3e773ab9b39268abddca002 Author: Nicola Paolucci <npaolucci@atlassian.com> Date: Tue Sep 29 15:27:35 2015 +0200 Squashed ‘src/sub-project‘ content from commit df563ed git-subtree-dir: src/sub-project git-subtree-split: df563ed15fa6…6b2e95d3
- 8. Result of git subtree add commit 8fb507baf7b270c30c822b27e262d0b44819b4c5 Merge: 606cd3e ab54c4e Author: Nicola Paolucci <npaolucci@atlassian.com> Date: Tue Sep 29 15:27:35 2015 +0200 Merge commit 'ab54c4e0b75c3107e3e773ab9b39268abddca002' as '.vim/bundle/fireplace' commit ab54c4e0b75c3107e3e773ab9b39268abddca002 Author: Nicola Paolucci <npaolucci@atlassian.com> Date: Tue Sep 29 15:27:35 2015 +0200 Squashed '.vim/bundle/fireplace/' content from commit df563ed git-subtree-dir: .vim/bundle/fireplace git-subtree-split: df563ed15fa685ce2508bf16b3ca7e176b2e95d3
- 9. To keep the sub-project up to date git subtree pull --prefix target-folder https://bitbucket.org/team/sub.git master --squash Command to pull project Folder where to insert code Repository URL v1.5
- 10. Under the hood of git subtree commit ab54c4e0b75c3107e3e773ab9b39268abddca002 Author: Nicola Paolucci <npaolucci@atlassian.com> Date: Tue Sep 29 15:27:35 2015 +0200 Squashed ‘src/sub-project‘ content from commit df563ed git-subtree-dir: src/sub-project git-subtree-split: df563ed15fa6…6b2e95d3
- 11. Find the symbolic ref matching a hash (sha-1) sha-1 of last commit pulled Git plumbing to list all remote refs Repository URL git ls-remote https://bitbucket.org/team/sub.git | grep df563ed df563ed15fa685ce2508bf16b3ca7e176b2e95d3 v1.1 5eaff1232acedeca565er7e1333234dacccebfff v1.5 git ls-remote https://bitbucket.org/team/sub.git | grep <sha-1>
- 12. Aliases to make your life easier! [alias] sba = "!f() { git subtree add --prefix $2 $1 master --squash; }; f" sbu = "!f() { git subtree pull --prefix $2 $1 master --squash; }; f" Alias section of your .gitconfig http://bit.do/git-aliases
- 13. How to use the aliases git sba <repo URL> <destination-folder> git sba https://bitbucket.org/team/sub.git src/sub
- 14. When everyone in the team must work on sub-projects When you have constant updates to your dependencies When you have many dependencies When NOT to use git subtree
- 15. For complex project dependencies Use a dependency tool. Really.
- 16. Alternatives? Read my rant on project dependencies http://bit.do/git-dep
- 17. How to extract a project Let’s learn how to use subtree split
- 18. Git subtree to extract a project Command to split out project git subtree split --prefix my/project/ --branch extracted Folder prefix to extract where we store it
- 19. Push to new remote We can remove the contents of the folder from the repo Import extracted branch Initialise a new repo and import the extracted branch Remove from old repo After we imported the code we can push it to a new repository git rm -rf my/project git init git pull ../path/ extracted git remote add origin … git push origin -u master
- 20. Interactive commit Splitting commits semantically in flight!
- 21. Fine grained control on your commits Knowing this technique frees you from worrying about what to do first Atomic commits make your changes readable Why split changes interactively?
- 22. We modify a single file (README) in 3 parts # Title Content of my article ## Subtitle second heading Some more paragraph content ## Conclusions
- 23. We modify a single file in 3 different parts [:~/p/demo] master(+3/-0) ± git diff @@ -1,11 +1,14 @@ # Title Content of my article +Adding a second line to Title. ## Subtitle second heading Some more paragraph content +Adding another line to Subtitle 1 ## Conclusions Here are your conclusions
- 24. To split those changes in separate commits: git commit --interactive staged unstaged path 1: unchanged +3/-0 README.md *** Commands *** 1: status 2: update 3: revert 4: add untracked 5: patch 6: diff 7: quit 8: help What now>
- 25. Overview of interactive staging revert The status of the files, whether they are staged or unstaged. update Choose which files to add to the staging area status Undo any action done previously in this session.
- 26. Overview of interactive staging [2] add untracked Check the unstaged or staged changes in the workspace. patch Add parts of a file to the staging area. This allows you to split commits. diff Add new untracked files to the repository.
- 27. I finally hit “p” for patch, select the file and ENTER: What now> p staged unstaged path 1: unchanged +3/-0 README.md Patch update>> 1 staged unstaged path * 1: unchanged +3/-0 README.md Patch update>>
- 28. I finally hit “p” for patch, select the file and ENTER: @@ -1,11 +1,14 @@ # Title Content of my article +Adding a second line to Title. ## Subtitle second heading Some more paragraph content +Adding another line to Subtitle 1 ## Conclusions Here are your conclusions +Adding to the Conclusions. Stage this hunk?!?!
- 30. A hunk is just a piece of text in a larger file. Diff and patch commands tend to understand changes by clustering them in blocks of continuous text. “ ”
- 32. If the default hunk size is too big, you can split it: Stage this hunk [y,n,q,a,d,/,s,e,?]? s Split into 3 hunks. @@ -1,7 +1,8 @@ # Title Content of my article +Adding a second line to Title. ## Subtitle second heading Some more paragraph content
- 33. Let’s stage this hunk, or add it to the staging area: Stage this hunk [y,n,q,a,d,/,j,J,g,e,?]? y @@ -4,8 +5,9 @@ ## Subtitle second heading Some more paragraph content +Adding another line to Subtitle 1 ## Conclusions Here are your conclusions Stage this hunk [y,n,q,a,d,/,K,j,J,g,e,?]?
- 34. Now so skip all the rest pressing “q” twice:
- 35. The result is a neat new commit and the rest left: 14a0be4 [4 minutes ago] (HEAD -> master) Add content to Title [Nick] git diff diff --git i/README.md w/README.md index fc26295..0ef85c4 100644 --- i/README.md +++ w/README.md @@ -6,7 +6,9 @@ Adding a second line to Title. ## Subtitle second heading Some more paragraph content +Adding another line to Subtitle 1 ## Conclusions
- 36. When you need help just press “?” Stage this hunk [y,n,q,a,d,/,s,e,?]? ? y - stage this hunk n - do not stage this hunk q - quit; do not stage this hunk or any of the remaining ones a - stage this hunk and all later hunks in the file d - do not stage this hunk or any later hunks in the file g - select a hunk to go to / - search for a hunk matching the given regex j - leave this hunk undecided, see next undecided hunk J - leave this hunk undecided, see next hunk k - leave this hunk undecided, see previous undecided hunk K - leave this hunk undecided, see previous hunk s - split the current hunk into smaller hunks e - manually edit the current hunk
- 38. Cross VCS mergesUnify two reposFast migration from svn Why collate history? Migrate immediately from Subversion, attach the earlier history after the migration. You have two repositories that should actually be only one. You need to perform Subversion merges in a Git branch
- 39. One relevant example: Linux kernel Today use git replace The entire history of the Linux kernel is split over three different repos. Originally in Grafts Which are local pair of ids connecting a commit id (SHA-1) to the next Linux kernel is split Available in the stock git distribution since version 1.6.5
- 40. git replace is capable to replace any object with any other object. It tracks these swaps via refs which you can push and pull between repositories. “ ”
- 41. git replace in practice shallow first last legacy shallow clone with cut history git replace first last
- 42. First commit of restarted repo git checkout -b shallow origin/shallow git log --max-parents=0 master git tag 56eacf first -m”Tag… commit” shallow first
- 43. Last commit of legacy repo git checkout -b legacy origin/legacy git rev-parse --verify legacy git tag 84abb last -m”Tag… commit” last legacy
- 44. git replace in practice shallow first last legacy shallow clone with cut history git replace first last
- 45. Replacements are persisted cat .git/refs/replace/56eac…7cc 84abb39d9aab234dfba2e41f13f693fa5edbfe22 git push origin ‘refs/replace/*’
- 46. If you want to make the git replace changes permanent and free the team from pulling those refs, do a final pass using git filter-branch “ ”
- 47. Go forth and enrich your Git experience
- 48. Thank you! NICOLA PAOLUCCI • DEVELOPER INSTIGATOR • ATLASSIAN • @DURDN Twitter: @durdn
- 49. • GIF backdrops taken from giphy.com • Icons from thenounproject.com credits below Image credits