LQF-24 documentation on project update (#14)

* Adding instructions on project update

* Fix typo error

* Add fetch tag section

* formatting correction

Co-authored-by: Maude Cahuet <[email protected]>
Co-authored-by: Lan Huong Mai <[email protected]>

README.md

@@ -36,4 +36,33 @@ Or, if you prefer to keep what you made, you can continue working on a new branc
 
  git checkout exercise-5-solution -b my-new-branchname
 
+## Update the project
+
+Project solutions are managed with tags.
+To update the project correctly I strongly recommend you to make multiple commits rather than a big one.
+The reason is that there is a script in the project `retag.sh` that is creating all solutions tags according git log history. 
+So to be sure that the modification you have done are in the correct exercise and tags you should follow those steps:
+
+1. Make your changes in a dedicated branch that will be merged into main.
+2. Once the branch is merged go on main branch and start an interactive rebase with this command: `git rebase -i --root` 
+the `--root` allow you to rebase from the first commit of the project.
+3. Place your modification commits where they belong. So for example a modification on exercise instruction should be 
+placed after the first commit (it will be squash), and a modification on exercise solution should be placed 
+after the commit of the exercise solution (e.g. Solution of Exercise 7).
+4. When every commit are in place change the verb at the start of the line from `pick` to `fixup` it will squash 
+with the precedent commit and keep the old commit message (to allow retag.sh to do it's job).
+5. After this you can save and quit interactive rebase
+6. Now your git history is clean and should be as the same as before. You can now execute `retag.sh`.
+7. Now you can push your branch and tags by doing `git push -f` and `git push -f --tags `.
+
+If the project has been updated and you want to fetch the new exercises tags : 
+
+1. git fetch --force --tags
+2. git pull --force --tags
+
+ or 
+1. remove the tags locally: git tag -l | xargs git tag -d
+2. fetch the tags : git fetch --tags
+
+Thanks for your contribution !