[doc] default readme page

git/readme.md

+
+## Command line instructions
+
+You can also upload existing files from your computer using the instructions below.
+Git global setup
+
+```
+git config --global user.name "Perfect Johnny"
+git config --global user.email "johnny.perfect@isae.fr"
+```
+
+## Create a new repository (johnny-project)
+
+```
+git clone git@gitlab.isae-supaero.fr:saclab/dss/students/johnny-project.git
+cd default-page
+touch README.md
+git add README.md
+git commit -m "[doc] add README"
+git push -u origin master
+```
+
+## Push an existing folder
+
+```
+cd existing_folder
+git init
+git remote add origin git@gitlab.isae-supaero.fr:saclab/dss/students/johnny-project.git
+git add .
+git commit -m "[doc] Initial commit"
+git push -u origin master
+```
+
+## Push an existing Git repository
+
+```
+cd existing_repo
+git remote rename origin old-origin
+git remote add origin git@gitlab.isae-supaero.fr:saclab/dss/students/johnny-project.git
+git push -u origin --all
+git push -u origin --tags
+```
+