Add tutorial on refactoring ISIS apps and tests (#73)

* Add tutorial on refactoring ISIS apps and tests

* Link setup urls instead

* Addressed some feedback

* Add find command

docs/how-to-guides/isis-developer-guides/building-and-contributing-to-isis-tutorial.md

+# Building and Contributing to ISIS Tutorial
+
+## 1. Set Up Your Local ISIS Environment
+
+Follow these tutorials to set up your local ISIS environment before you get started:
+
+1. [Getting Started With GitHub](https://astrogeology.usgs.gov/docs/how-to-guides/isis-developer-guides/developing-isis3-with-cmake/#getting-started-with-github)
+2. [Anaconda and ISIS3 Dependencies](https://astrogeology.usgs.gov/docs/how-to-guides/isis-developer-guides/developing-isis3-with-cmake/#anaconda-and-isis3-dependencies)
+3. [Building ISIS3](https://astrogeology.usgs.gov/docs/how-to-guides/isis-developer-guides/developing-isis3-with-cmake/#building-isis3)
+
+## 2. Converting Apps and Tests
+
+Once you have ISIS built, find apps that still have the old test setup by running:
+
+```
+find isis/src/*/apps/ -regex '.*/tsts' | sed 's:[^/]*$::'
+```
+
+Apps that need to be refactored only have *app-name.xml* and *main.cpp*, other than the *Makefile* and other possible folders (like `assets` and `tsts`). Take a look at the [bandtrim](https://github.com/DOI-USGS/ISIS3/tree/dev/isis/src/base/apps/bandtrim) app for example. In comparison, apps that have been updated to fit the gtest suite will have *app-name.xml*, *app-name.cpp*, *app-name.h*, and *main.cpp*, like the [campt](https://github.com/DOI-USGS/ISIS3/tree/dev/isis/src/base/apps/campt) app.
+
+After finding a suitable app to refactor, follow the steps in [Refactoring ISIS3 Applications](https://astrogeology.usgs.gov/docs/how-to-guides/isis-developer-guides/writing-isis-tests-with-ctest-and-gtest/#refactoring-isis3-applications) in your selected app.
+
+To write a new test suite with gtest, follow the steps in [Creating a new test suite](https://astrogeology.usgs.gov/docs/how-to-guides/isis-developer-guides/writing-isis-tests-with-ctest-and-gtest/#creating-a-new-test-suite). 
+
+A great way to get a grasp on the converting process is by looking at previous examples so here are some PRs:
+
+- [`gaussstretch` PR #5259](https://github.com/DOI-USGS/ISIS3/pull/5259)
+- [`skypt` PR #5444](https://github.com/DOI-USGS/ISIS3/pull/5444)
+  
+## 3. Run Tests
+
+Check out [Running Tests](https://astrogeology.usgs.gov/docs/how-to-guides/isis-developer-guides/developing-isis3-with-cmake/#running-tests) to get an idea on how to run your tests.
+
+As an example, let's look at the [`skypt` test suite](https://github.com/DOI-USGS/ISIS3/blob/dev/isis/tests/FunctionalTestsSkypt.cpp). You can run the all of `skypt`'s tests with `ctest -R skypt`. Let's say you want to test only the first test case in *FunctionalTestsSkypt.cpp*, run `ctest -R FunctionalTestSkyptDefault`. 
+
+## 4. Update CHANGELOG
+
+Make sure you update the *CHANGELOG.md* located in the root of the `ISIS3` folder by adding an entry under the **Unreleased** heading and **Changed** subheading.
+
+## 5. Create PR
+
+Once your tests are in good shape with passing marks, let's create a Pull Request (PR). Go to your forked ISIS3 repo page and select the **Pull requests** tab towards the top of the page. Then, hit the green **New pull request** button which will take you to a page where you select your base and head repositories to compare before creating the pull request. The base repository is the repo you will be pushing your changes *to*, so it should be set to 
+```
+base repository: **DOI-USGS/ISIS3**, base: **dev**
+```
+
+The head repository is where the changes will be coming *from*, a.k.a. where you have been pushing your local changes to:
+```
+head repository: **<your-account-name>/ISIS3**, compare: **<branch-name>**
+```
+
+Check the changes on the comparison page then hit the green **Create pull request** button. You will have the opportunity to make more changes to your branch after creating the PR so no worries if you are unable to catch something in this stage. 
+
+Now, you should be on a page titled **Open a pull request**, the step to add further details regarding your PR. Under **Add a title**, title your PR as *APP-NAME app and tests refactor* (e.g., *gaussstretch app and tests refactor*).
+
+In the body of the PR, there should already be a PR template ready for you to fill out, you can check out the preview of what the PR would look like when created when you select the **Preview** tab. Here's a general outline in what the PR should look like:
+
+```md
+**Description**
+Describe what app, tests, and any appropriate files have been affected. 
+You can also note any weird quirks or changes to the main code that seemed necessary to give the reviewer more context.
+
+**Related Issue**
+Usually, you would add here *Addresses <issue-url>*. 
+If there is no existing GitHub issue to link, you can leave this blank.
+
+**How Has This Been Validated?**
+Write down related ctest commands so that the reviewer can test the PR.
+
+**Types of changes**
+Checkmark the *New feature* item.
+
+**Checklist**
+Go through the checklist and mark them as you go.
+Some of them may not be necessary in this case so keep that in mind.
+
+**Licensing**
+Accept the terms by checking the box once you have read through this portion.
+```
+
+Complete the pull request process by clicking the green **Create pull request** button under the body of the PR. This will open a PR that is viewable by everyone.
+
+Finally, add this comment on your PR to notify Astro developers that your PR is ready for review:
+
+```
+@DOI-USGS/astrogeology-developers, ready for review
+```

mkdocs.yml

@@ -76,6 +76,7 @@ nav:
       - Class Requirements For Using Doxygen Tags:    how-to-guides/isis-developer-guides/class-requirements-for-using-doxygen-tags.md
       - Developing ISIS3 with cmake:                  how-to-guides/isis-developer-guides/developing-isis3-with-cmake.md
       - ISIS Development on the Mac M1 ARM System:    how-to-guides/isis-developer-guides/developing-mac-m1-arm-systems.md
+      - Building and Contributing to ISIS Tutorial:   how-to-guides/isis-developer-guides/building-and-contributing-to-isis-tutorial.md
       - Obtaining, Maintaining, and Submitting Test Data: how-to-guides/isis-developer-guides/obtaining-maintaining-submitting-test-data.md
       - ISIS Programming Exercises:
         - Exercise 1:                                 how-to-guides/isis-developer-guides/exercise-1.md