Add some examples (#1821)

* Adds some examples

* Run rustfmt

* Fixed a few descriptions in the examples

crates/nu-cli/src/commands/open.rs

@@ -43,6 +43,13 @@ impl WholeStreamCommand for Open {
     ) -> Result<OutputStream, ShellError> {
         open(args, registry)
     }
+
+    fn examples(&self) -> &[Example] {
+        &[Example {
+            description: "Opens \"users.csv\" and creates a table from the data",
+            example: "open users.csv",
+        }]
+    }
 }
 
 fn open(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {

crates/nu-cli/src/commands/reject.rs

@@ -32,6 +32,13 @@ impl WholeStreamCommand for Reject {
     ) -> Result<OutputStream, ShellError> {
         reject(args, registry)
     }
+
+    fn examples(&self) -> &[Example] {
+        &[Example {
+            description: "Lists the files in a directory without showing the modified column",
+            example: "ls | reject modified",
+        }]
+    }
 }
 
 fn reject(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {

crates/nu-cli/src/commands/touch.rs

@@ -34,7 +34,15 @@ impl WholeStreamCommand for Touch {
     ) -> Result<OutputStream, ShellError> {
         touch(args, registry)
     }
+
+    fn examples(&self) -> &[Example] {
+        &[Example {
+            description: "Creates \"fixture.json\"",
+            example: "touch fixture.json",
+        }]
+    }
 }
+
 fn touch(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
     let registry = registry.clone();
     let stream = async_stream! {

crates/nu-cli/src/commands/trim.rs

@@ -26,6 +26,13 @@ impl WholeStreamCommand for Trim {
     ) -> Result<OutputStream, ShellError> {
         trim(args, registry)
     }
+
+    fn examples(&self) -> &[Example] {
+        &[Example {
+            description: "Trims surrounding whitespace and outputs \"Hello world\"",
+            example: "echo \"    Hello world\" | trim",
+        }]
+    }
 }
 
 fn trim_primitive(p: &mut Primitive) {

crates/nu-cli/src/commands/version.rs

@@ -26,6 +26,13 @@ impl WholeStreamCommand for Version {
     ) -> Result<OutputStream, ShellError> {
         version(args, registry)
     }
+
+    fn examples(&self) -> &[Example] {
+        &[Example {
+            description: "Display Nu version",
+            example: "version",
+        }]
+    }
 }
 
 pub fn version(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {

crates/nu-cli/src/commands/where_.rs

@@ -36,6 +36,27 @@ impl WholeStreamCommand for Where {
     ) -> Result<OutputStream, ShellError> {
         where_command(args, registry)
     }
+
+    fn examples(&self) -> &[Example] {
+        &[
+            Example {
+                description: "List all files in the current directory with sizes greater than 2kb",
+                example: "ls | where size > 2kb",
+            },
+            Example {
+                description: "List only the files in the current directory",
+                example: "ls | where type == File",
+            },
+            Example {
+                description: "List all files with names that contain \"Car\"",
+                example: "ls | where name =~ \"Car\"",
+            },
+            Example {
+                description: "List all files that were modified in the last two months",
+                example: "ls | where modified <= 2M",
+            },
+        ]
+    }
 }
 fn where_command(
     raw_args: CommandArgs,