The baNaNa Git project

This repository serves as a demo project for the baNaNa hands-on session for the SIAM Student Chapter Delft given at TU Delft on 22-02-2018.

Github repository https://github.com/mmoelle1/banana-git.git

Tutorial 1: Setup your local git configuration

To work efficiently with git at the command line it is quite handy to add the following configuration to your global ~/.gitconfig file

[alias]
  br = branch
  ci = commit
  co = checkout
  st = status
  log1 = log --oneline
  log2 = log --name-status
  log3 = log --name-status --pretty=fuller
  log4 = log --stat
  log5 = log -p --full-diff
  logsincebranchbase = log master...@{0}
  squash-all = "!f(){ git reset $(git commit-tree HEAD^{tree} -m \"${1:-Initial commit}\");};f"
[color]
  branch = auto
  diff = auto
  interactive = auto
  status = auto
[user]
  name = Your Name
  email = [email protected]
[core]
  excludesfile = ~/.gitignore_global

Moreover, it is a good idea to define a global list of file extensions that should be ignored by git in the global file ~/.gitignore_global

*.acn
*.acr
*.alg
*.aux
*.bbl
*.bcf
*.blg
*.dvi
*.glg
*.glo
*.gls
*.idx
*.ilg
*.ind
*.ist
*.lof
*.log
*.lot
*.maf
*.mod
*.mtc
*.mtc1
*.nav
*.o
*.out
*.snm
*.swp
*.synctex.gz
*.toc
*.vrb
*~
.DS_Store

Tutorial 2: Getting started wit Github

To reproduce the steps shown during the hands-on sessions follow these steps:

1. Create a free account at https://github.com

2. Clone the project https://github.com/mmoelle1/banana-git.git to your local disk by running in the terminal

   git clone https://github.com/mmoelle1/banana-git.git
   

Tutorial 3: Merging and resolving conflicts

Git helps you to merge your work with the work of your colleagues working on the same project. Whenever Git is able to merge all changes automatically it will do so. However, if two (or more) people change the same file at the same location so that it is not clear which change should override the other one then Git needs your manual input.

1. In the web frontend of Github we modify the last line of the file demo.m to

   plot(y,x)
   

   and commit the changes to the repository by clicking the Commit button.

2. In the local checkout of the repository we modify the last line of the file demo.m to

   plot(y,x)
   

   and commit the changes to the repository by running in the terminal

   git ci -m "Changing demo.m"
   

   without having updated the local checkout of the repository before.

3. This results in a merge conflict that cannot be solved automatically

   Auto-merging demo.m
   CONFLICT (content): Merge conflict in demo.m
   Automatic merge failed; fix conflicts and then commit the result.
   

   If we look into the file demo.m we find

   <<<<<<< HEAD
   plot(x,x)
   =======
   plot(y,x)
   >>>>>>> fa5516bc91ddea24be32b3b238b7a9734e60698f
   

4. Let us decide to keep the version plot(y,x) and commit the changes by running in the terminal

   git ci
   

Tutorial 4: Branching and pull requests

Branches allow you to develop several features independently from each other without "polluting" the master branch.

1. In the web frontend of Github we create a new branch testing.

2. Next we update our local checkout by running in the terminal

   git pull
   

3. Our local checkoput now shows the different branches

   git br -a
   
   * master
   remotes/origin/HEAD -> origin/master
   remotes/origin/testing
   remotes/origin/master
   

4. We switch to the testing branch by running in the terminal

   git co -b testing origin/testing
   

5. This will create the local branch testing from the remote branch origin/testing. Let us create a new file and commit it to the testing branch.

   echo "demo(10)" > run.m
   git add run.m
   git ci -m "Added new file run.m"
   git push
   

6. This file has been committed to the testing branch and is not available in the master branch (check this via the web frontend). To merge the commit into the master branch we create a so-called pull request via the web frontend.

7. We can accept the pull request via the web frontend to physically merge the commit into the master branch. Verify that the file run.m is in the master branch.

8. If you are the owner of the project you might want to prevent direct commits to the master branch at all. You can enable this feature in Settings->Branches by addint the master branch to the list of protected branches and activete the check boxes Protect this branch and Require pull request reviews before merging.

Tutorial 5: Creating formatted patches

Git allows you to create formatted patches from your local commits that can be shared with colleagues, e.g., via email. This makes it possible to develop a feature incrementally with different programmers and only commit the final version to the Git repository.

1. Let us first create a new file demo2.m

   echo "function [x,y] = demo2(n) % DEMO x = linspace(0,1,n); y = sin(2*pi*x);" >> demo2.m
   

   add it to the local repository

   git add demo2.m
   

   and commit the changes

   git ci -m "Added file demo2.m"
   

2. The git log shows the following

   git log
   
   commit 1e4b5346cba92df983bcca375fb370677dd26600 (HEAD -> testing)
   Author: Matthias Moeller <[email protected]>
   Date:   Thu Feb 22 15:58:25 2018 +0100
   
       Added file demo2.m
   
   commit 221a2c2bc79ec21f89c1058b25c53f54b666b86c (origin/Testing)
   Author: Matthias Moeller <[email protected]>
   Date:   Thu Feb 22 15:48:38 2018 +0100
   
       Updated README.md
   
   commit 40ecd57a66b1340e0a8de95e9b4c3b44e056925b
   Author: Matthias Moeller <[email protected]>
   Date:   Thu Feb 22 15:39:46 2018 +0100
   
       Added new file run.m
   
   commit 3883e04efa1da649d8303a61294208e197ec94c0 (origin/master, origin/HEAD, master)
   Author: Matthias Moeller <[email protected]>
   Date:   Wed Feb 21 23:03:18 2018 +0100
   
       Updated README.md
   
   commit 9b50fcd6527b96a17f406b7a43c77758d98bf7ad
   Author: Matthias Moeller <[email protected]>
   Date:   Wed Feb 21 22:57:38 2018 +0100
   
       Updated README.md
   
   ...
   

3. Instead of pushing the local changes to the global repository, we let git generate a formatted patch file

   git format-patch 221a2c2bc79ec21f89c1058b25c53f54b666b86c
   

   which is

   0001-Added-file-demo2.m.patch
   

   and send this file, e.g., via email to our colleague.

4. Our colleague can apply this patch to his local checkout

   git am 0001-Added-file-demo2.m.patch
   

   and now has the same state is we have.

5. Assume that multiple patches have been sent back and force unti a stable version of the code has been reached.

   git log
   
   commit c439af4ccea143a25ef5cd51a1b60a71e7abc77f (HEAD -> testing)
   Author: Matthias Moeller <[email protected]>
   Date:   Thu Feb 22 16:04:02 2018 +0100
   
       Updated demo2.m
   
   commit 1e4b5346cba92df983bcca375fb370677dd26600
   Author: Matthias Moeller <[email protected]>
   Date:   Thu Feb 22 15:58:25 2018 +0100
   
       Added file demo2.m
   

6. Instead of committing all local development steps to the global repository we can combine them into a single commit.

   git rebase -i HEAD~5
   

   This shows you the last five commits starting at the latest one (HEAD)

   pick 3883e04 Updated README.md
   pick 40ecd57 Added new file run.m
   pick 221a2c2 Updated README.md
   pick 1e4b534 Added file demo2.m
   pick c439af4 Updated demo2.m
   
   # Rebase 9b50fcd..c439af4 onto 9b50fcd (5 commands)
   #
   # Commands:
   # p, pick = usecommit
   # 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
   # d, drop = remove commit
   #
   # These lines can be re-ordered; they are executed from top to bottom.
   #
   # If you remove a line here THAT COMMIT WILL BE LOST.
   #
   # However, if you remove everything, the rebase will be aborted.
   #
   

7. We simply want to combine the last to commits so we change the last two lines to

   e 1e4b534 Added file demo2.m
   s c439af4 Updated demo2.m
   

   This will meld the last commit into the previous one and, moreover, allow us to edit the commit message.

8. When exiting the editor git offers the following possibilities

   Stopped at 1e4b534...  Added file demo2.m
   You can amend the commit now, with
   
     git commit --amend 
   
   Once you are satisfied with your changes, run
   
     git rebase --continue
   

9. We decide that we are satisfied with the changes and run

   git rebase --continue
   

10. Finally, we adjust the commit message and push the final commit to the global repository

    git push
    

Tutorial 6: Merging entire branches

Notice that we have done all previous changes in the testing branch. Instead of creating pull requests we can also merge the entire testing branch with the master branch.

1. Let is first switch back to the master branch

   git co master
   

   and update it to the latest version from the global repository

   git pull
   

2. Next, we merge the testing branch with the master branch

   git merge testing
   

3. Finally, we push the local changes in the master branch to the global repository

   git push