Fix inaccurate links in Tutorial: Adding a command (AY2122S2-CS2103T-…

…T12-4#117)

There are links in the tutorial that do not point to the specific
section of the commit that the tutorial refers to.

Let's change those links to avoid confusion.

docs/tutorials/AddRemark.md

@@ -45,7 +45,7 @@ public class RemarkCommand extends Command {
 
 Now that we have our `RemarkCommand` ready to be executed, we need to update `AddressBookParser#parseCommand()` to recognize the `remark` keyword. Add the new command to the `switch` block by creating a new `case` that returns a new instance of `RemarkCommand`.
 
-You can refer to the changes in this [diff](https://github.com/se-edu/addressbook-level3/commit/35eb7286f18a029d39cb7a29df8f172a001e4fd8#diff-34ace715a8a8d2e5a66e71289f017b47).
+You can refer to the changes in this [diff](https://github.com/se-edu/addressbook-level3/commit/35eb7286f18a029d39cb7a29df8f172a001e4fd8#diff-399c284cb892c20b7c04a69116fcff6ccc0666c5230a1db8e4a9145def8fa4ee).
 
 ### Run the application
 
@@ -136,7 +136,7 @@ public class RemarkCommand extends Command {
 }
 ```
 
-Your code should look something like [this](https://github.com/se-edu/addressbook-level3/commit/35eb7286f18a029d39cb7a29df8f172a001e4fd8#diff-34ace715a8a8d2e5a66e71289f017b47) after you are done.
+Your code should look something like [this](https://github.com/se-edu/addressbook-level3/commit/dc6d5139d08f6403da0ec624ea32bd79a2ae0cbf#diff-a8e35af8f9c251525063fae36c9852922a7e7195763018eacec60f3a4d87c594) after you are done.
 
 ### Parse user input
 
@@ -221,7 +221,7 @@ public RemarkCommand parse(String args) throws ParseException {
 </div>
 
 If you are stuck, check out the sample
-[here](https://github.com/se-edu/addressbook-level3/commit/dc6d5139d08f6403da0ec624ea32bd79a2ae0cbf#diff-fc19ecee89c3732a62fbc8c840250508).
+[here](https://github.com/se-edu/addressbook-level3/commit/dc6d5139d08f6403da0ec624ea32bd79a2ae0cbf#diff-8bf239e8e9529369b577701303ddd96af93178b4ed6735f91c2d8488b20c6b4a).
 
 ## Add `Remark` to the model
 
@@ -231,7 +231,7 @@ Now that we have all the information that we need, let’s lay the groundwork fo
 
 Create a new `Remark` in `seedu.address.model.person`. Since a `Remark` is a field that is similar to `Address`, we can reuse a significant bit of code.
 
-A copy-paste and search-replace later, you should have something like [this](https://github.com/se-edu/addressbook-level3/commit/4516e099699baa9e2d51801bd26f016d812dedcc#diff-af2f075d24dfcd333876f0fbce321f25). Note how `Remark` has no constrains and thus does not require input
+A copy-paste and search-replace later, you should have something like [this](https://github.com/se-edu/addressbook-level3/commit/4516e099699baa9e2d51801bd26f016d812dedcc#diff-41bb13c581e280c686198251ad6cc337cd5e27032772f06ed9bf7f1440995ece). Note how `Remark` has no constrains and thus does not require input
 validation.
 
 ### Make use of `Remark`
@@ -242,7 +242,7 @@ Let’s change `RemarkCommand` and `RemarkCommandParser` to use the new `Remark`
 
 Without getting too deep into `fxml`, let’s go on a 5 minute adventure to get some placeholder text to show up for each person.
 
-Simply add the following to [`seedu.address.ui.PersonCard`](https://github.com/se-edu/addressbook-level3/commit/850b78879582f38accb05dd20c245963c65ea599#diff-0c6b6abcfac8c205e075294f25e851fe).
+Simply add the following to [`seedu.address.ui.PersonCard`](https://github.com/se-edu/addressbook-level3/commit/850b78879582f38accb05dd20c245963c65ea599#diff-639834f1e05afe2276a86372adf0fe5f69314642c2d93cfa543d614ce5a76688).
 
 **`PersonCard.java`:**
 
@@ -254,7 +254,7 @@ private Label remark;
 
 `@FXML` is an annotation that marks a private or protected field and makes it accessible to FXML. It might sound like Greek to you right now, don’t worry — we will get back to it later.
 
-Then insert the following into [`main/resources/view/PersonListCard.fxml`](https://github.com/se-edu/addressbook-level3/commit/850b78879582f38accb05dd20c245963c65ea599#diff-12580431f55d7880578aa4c16f249e71).
+Then insert the following into [`main/resources/view/PersonListCard.fxml`](https://github.com/se-edu/addressbook-level3/commit/850b78879582f38accb05dd20c245963c65ea599#diff-d44c4f51c24f6253c277a2bb9bc440b8064d9c15ad7cb7ceda280bca032efce9).
 
 **`PersonListCard.fxml`:**
 
@@ -373,7 +373,7 @@ Tests are crucial to ensuring that bugs don’t slip into the codebase unnoticed
 
 Let’s verify the correctness of our code by writing some tests!
 
-Of course you can simply add the test cases manually, like you've been doing all along this tutorial. The result would be like the test cases in [here](https://github.com/se-edu/addressbook-level3/commit/fac8f3fd855d55831ca0cc73313b5943d49d4d6e#diff-d749de38392f7ea504da7824641ba8d9). Alternatively, you can get the help of IntelliJ to generate the skeletons of the test cases, as explained in the next section.
+Of course you can simply add the test cases manually, like you've been doing all along this tutorial. The result would be like the test cases in [here](https://github.com/se-edu/addressbook-level3/commit/fac8f3fd855d55831ca0cc73313b5943d49d4d6e#diff-ff58f7c10338b34f76645df49b71ecb2bafaf7611b20e7ff59ebc98475538a01). Alternatively, you can get the help of IntelliJ to generate the skeletons of the test cases, as explained in the next section.
 
 ### Automatically generating tests
 
@@ -394,7 +394,7 @@ Following convention, let’s change the name of the generated method to `execut
 
 Let’s use the utility functions provided in `CommandTestUtil`. The functions ensure that commands produce the expected `CommandResult` and output the correct message. In this case, `CommandTestUtil#assertCommandSuccess` is the best fit as we are testing that a `RemarkCommand` will successfully add a `Remark`.
 
-You should end up with a test that looks something like [this](https://github.com/se-edu/addressbook-level3/commit/fac8f3fd855d55831ca0cc73313b5943d49d4d6e#diff-d749de38392f7ea504da7824641ba8d9).
+You should end up with a test that looks something like [this](https://github.com/se-edu/addressbook-level3/commit/fac8f3fd855d55831ca0cc73313b5943d49d4d6e#diff-ff58f7c10338b34f76645df49b71ecb2bafaf7611b20e7ff59ebc98475538a01R36-R49).
 
 ## Conclusion