Update how_to_use_git.md

documentation/how_to_use_git.md

+# How to use Git
+This project uses Git. That means that if you plan to make any edits to the
+project, you'll be using some Git command.
+
+## Where is everything?
+Everything is on the master branch. In git, a _branch_ is like a timeline of
+the project. The timeline is composed of incremental changes, called _commits_.
+In the case of the master branch, these commits go all the way back to the
+beginning of the project. Nobody can delete history on the master branch. Once a
+commit is added, it is permanent. When you browse files on Gitlab, you are
+likely looking at the most recent state of the master branch.
+
+## How do I make changes?
+To make a change to the project, you'll need to make a commit to the master
+branch. You can technically make edits to files right in Gitlab, but most
+people prefer to copy the entire Git project locally to their PC, make
+edits, and then copy those changes back to the main Git project on Gitlab.
+
+### Using your own computer to make changes
+#### Setup (Only need to do once)
+First, [setup an SSH key](https://git.ece.iastate.edu/help/ssh/README).
+
+Clone the project:
+```
+git clone git@git.ece.iastate.edu:danc/MicroCART.git
+```
+That was easy. You can enter the directory you just made, and see all of the
+project files.
+
+#### Actually making changes
+First, sync to be sure your personal computer has the most recent state of
+master on Gitlab.
+```
+git pull origin master
+```
+Now you can make your edits. Do whatever you like to the project.
+
+When you are finished, look over the changes you have made.
+```
+git status
+git diff
+```
+If you are happy with you changes, it is time to prepare a commit.
+
+Stage each changed file in order to commit them:
+```
+git add (name your files here)
+```
+If you don't want list out every file you changed, you can do clever things
+like using the entire folder where the changed files are (sometimes people will
+use `.` for the current directory).
+
+Look at the files you have staged:
+```
+git status
+```
+
+If all looks well, it is time to commit:
+```
+git commit -m "describe your changes here"
+```
+If you'd prefer to use a text editor to write your commit message, drop the `-m`
+part.
+
+You can look at the commit you just made:
+```
+git commit log -n 3
+```
+
+Now we need to sync your master branch with the master branch on Gitlab.
+```
+git push origin master
+```
+
+It's likely someone else has made a change since your last sync, so you may get
+an error saying your master is out of date. In that case, sync your master with 
+Gitlab's master again.
+
+```
+git pull origin master
+```
+
+If you happend to be editing the same lines as someone else, you'll get the
+so-called "merge conflicts." In that case, look at the error output to determine
+which files have conflicts, and go edit those files. You'll have to choose which
+changes to keep. At the end of the day, you need to get rid of the `<<<` lines.
+Once you have fixed everything, `git add` those changes and `git commit` to
+create a merge commit. Maybe do another `git log` after everything to be sure
+everything makes sense.
+
+Once you have synced your master with Gitlab's master again, sync Gitlab's
+master with your master again:
+```
+git push origin master
+```
+
+If all succeeds, you should be able to see your commit on Gitlab.
+
+## Other workflows
+What we just described is the bare minimum Git workflow. Most people don't like
+working this way. We encourage you to research other workflows, like a Git
+branching workflow.