Auto merge of #21376 - JoshBrudnak:master, r=jdm

Add rustfmt command to devenv commands

Added the rustfmt command to devenv commands which runs cargo fmt on a specified directory.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #21374

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because they only included a simple command that was added to the devenv_commands python script.

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python/servo/devenv_commands.py

@@ -229,6 +229,19 @@ class MachCommands(CommandBase):
         with cd(self.context.topdir):
             return self.call_rustup_run(["cargo", "fetch"], env=self.build_env())
 
+    @Command('rustfmt',
+             description='Format the Rust code using Cargo fmt',
+             category='devenv')
+    @CommandArgument(
+        '--directory', '-d', default=None,
+        help='Command-line argument to specify the directory for formatting')
+    def rustfmt(self, directory=""):
+        if directory == "":
+            directory = self.context.topdir
+
+        with cd(self.context.topdir):
+            return self.call_rustup_run(["cargo", "fmt", "--", directory], env=self.build_env())
+
     @Command('ndk-stack',
              description='Invoke the ndk-stack tool with the expected symbol paths',
              category='devenv')