rust: replace most "operation" structs with functions The hg-core crate has a partially-formed concept of "operation", represented as structs with constructors and a `run` method. Each struct?s contructor takes different parameters, and each `run` has a different return type. Constructors typically don?t do much more than store parameters for `run` to access them. There was a comment about adding an `Operation` trait when the language supports expressing something so general, but it?s hard to imagine how operations with such different APIs could be used in a generic context. This commit starts removing the concept of "operation", since those are pretty much just functions. Differential Revision: https://phab.mercurial-scm.org/D9595

--- a/rust/rhg/src/commands/root.rs	Mon Dec 14 13:47:44 2020 +0100
+++ b/rust/rhg/src/commands/root.rs	Mon Dec 14 14:59:23 2020 +0100
@@ -2,7 +2,7 @@
 use crate::error::CommandError;
 use crate::ui::Ui;
 use format_bytes::format_bytes;
-use hg::operations::FindRoot;
+use hg::operations::find_root;
 use hg::utils::files::get_bytes_from_path;
 
 pub const HELP_TEXT: &str = "
@@ -21,7 +21,7 @@
 
 impl Command for RootCommand {
     fn run(&self, ui: &Ui) -> Result<(), CommandError> {
-        let path_buf = FindRoot::new().run()?;
+        let path_buf = find_root()?;
 
         let bytes = get_bytes_from_path(path_buf);