--- a/rust/rhg/src/commands/cat.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/commands/cat.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,14 +1,10 @@
 use crate::error::CommandError;
-use crate::ui::Ui;
 use clap::Arg;
-use clap::ArgMatches;
-use hg::config::Config;
 use hg::operations::cat;
 use hg::repo::Repo;
 use hg::utils::hg_path::HgPathBuf;
 use micro_timer::timed;
 use std::convert::TryFrom;
-use std::path::Path;
 
 pub const HELP_TEXT: &str = "
 Output the current or given revision of files
@@ -36,19 +32,14 @@
 }
 
 #[timed]
-pub fn run(
-    ui: &Ui,
-    config: &Config,
-    repo_path: Option<&Path>,
-    args: &ArgMatches,
-) -> Result<(), CommandError> {
-    let rev = args.value_of("rev");
-    let file_args = match args.values_of("files") {
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let rev = invocation.subcommand_args.value_of("rev");
+    let file_args = match invocation.subcommand_args.values_of("files") {
         Some(files) => files.collect(),
         None => vec![],
     };
 
-    let repo = Repo::find(config, repo_path)?;
+    let repo = Repo::find(invocation.non_repo_config, invocation.repo_path)?;
     let cwd = hg::utils::current_dir()?;
 
     let mut files = vec![];
@@ -67,7 +58,7 @@
     match rev {
         Some(rev) => {
             let data = cat(&repo, rev, &files).map_err(|e| (e, rev))?;
-            ui.write_stdout(&data)?;
+            invocation.ui.write_stdout(&data)?;
             Ok(())
         }
         None => Err(CommandError::Unimplemented.into()),

--- a/rust/rhg/src/commands/config.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/commands/config.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,13 +1,9 @@
 use crate::error::CommandError;
-use crate::ui::Ui;
 use clap::Arg;
-use clap::ArgMatches;
 use format_bytes::format_bytes;
-use hg::config::Config;
 use hg::errors::HgError;
 use hg::repo::Repo;
 use hg::utils::SliceExt;
-use std::path::Path;
 
 pub const HELP_TEXT: &str = "
 With one argument of the form section.name, print just the value of that config item.
@@ -25,20 +21,16 @@
         .about(HELP_TEXT)
 }
 
-pub fn run(
-    ui: &Ui,
-    config: &Config,
-    repo_path: Option<&Path>,
-    args: &ArgMatches,
-) -> Result<(), CommandError> {
-    let opt_repo = Repo::find_optional(config, repo_path)?;
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let opt_repo =
+        Repo::find_optional(invocation.non_repo_config, invocation.repo_path)?;
     let config = if let Some(repo) = &opt_repo {
         repo.config()
     } else {
-        config
+        invocation.non_repo_config
     };
-
-    let (section, name) = args
+    let (section, name) = invocation
+        .subcommand_args
         .value_of("name")
         .expect("missing required CLI argument")
         .as_bytes()
@@ -47,6 +39,6 @@
 
     let value = config.get(section, name).unwrap_or(b"");
 
-    ui.write_stdout(&format_bytes!(b"{}\n", value))?;
+    invocation.ui.write_stdout(&format_bytes!(b"{}\n", value))?;
     Ok(())
 }

--- a/rust/rhg/src/commands/debugdata.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/commands/debugdata.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,13 +1,9 @@
 use crate::error::CommandError;
-use crate::ui::Ui;
 use clap::Arg;
 use clap::ArgGroup;
-use clap::ArgMatches;
-use hg::config::Config;
 use hg::operations::{debug_data, DebugDataKind};
 use hg::repo::Repo;
 use micro_timer::timed;
-use std::path::Path;
 
 pub const HELP_TEXT: &str = "
 Dump the contents of a data file revision
@@ -42,12 +38,8 @@
 }
 
 #[timed]
-pub fn run(
-    ui: &Ui,
-    config: &Config,
-    repo_path: Option<&Path>,
-    args: &ArgMatches,
-) -> Result<(), CommandError> {
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let args = invocation.subcommand_args;
     let rev = args
         .value_of("rev")
         .expect("rev should be a required argument");
@@ -63,10 +55,10 @@
             }
         };
 
-    let repo = Repo::find(config, repo_path)?;
+    let repo = Repo::find(invocation.non_repo_config, invocation.repo_path)?;
     let data = debug_data(&repo, rev, kind).map_err(|e| (e, rev))?;
 
-    let mut stdout = ui.stdout_buffer();
+    let mut stdout = invocation.ui.stdout_buffer();
     stdout.write_all(&data)?;
     stdout.flush()?;
 

--- a/rust/rhg/src/commands/debugrequirements.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/commands/debugrequirements.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,9 +1,5 @@
 use crate::error::CommandError;
-use crate::ui::Ui;
-use clap::ArgMatches;
-use hg::config::Config;
 use hg::repo::Repo;
-use std::path::Path;
 
 pub const HELP_TEXT: &str = "
 Print the current repo requirements.
@@ -13,13 +9,8 @@
     clap::SubCommand::with_name("debugrequirements").about(HELP_TEXT)
 }
 
-pub fn run(
-    ui: &Ui,
-    config: &Config,
-    repo_path: Option<&Path>,
-    _args: &ArgMatches,
-) -> Result<(), CommandError> {
-    let repo = Repo::find(config, repo_path)?;
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let repo = Repo::find(invocation.non_repo_config, invocation.repo_path)?;
     let mut output = String::new();
     let mut requirements: Vec<_> = repo.requirements().iter().collect();
     requirements.sort();
@@ -27,6 +18,6 @@
         output.push_str(req);
         output.push('\n');
     }
-    ui.write_stdout(output.as_bytes())?;
+    invocation.ui.write_stdout(output.as_bytes())?;
     Ok(())
 }

--- a/rust/rhg/src/commands/files.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/commands/files.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,14 +1,11 @@
 use crate::error::CommandError;
 use crate::ui::Ui;
 use clap::Arg;
-use clap::ArgMatches;
-use hg::config::Config;
 use hg::operations::list_rev_tracked_files;
 use hg::operations::Dirstate;
 use hg::repo::Repo;
 use hg::utils::files::{get_bytes_from_path, relativize_path};
 use hg::utils::hg_path::{HgPath, HgPathBuf};
-use std::path::Path;
 
 pub const HELP_TEXT: &str = "
 List tracked files.
@@ -29,23 +26,18 @@
         .about(HELP_TEXT)
 }
 
-pub fn run(
-    ui: &Ui,
-    config: &Config,
-    repo_path: Option<&Path>,
-    args: &ArgMatches,
-) -> Result<(), CommandError> {
-    let rev = args.value_of("rev");
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let rev = invocation.subcommand_args.value_of("rev");
 
-    let repo = Repo::find(config, repo_path)?;
+    let repo = Repo::find(invocation.non_repo_config, invocation.repo_path)?;
     if let Some(rev) = rev {
         let files =
             list_rev_tracked_files(&repo, rev).map_err(|e| (e, rev))?;
-        display_files(ui, &repo, files.iter())
+        display_files(invocation.ui, &repo, files.iter())
     } else {
         let distate = Dirstate::new(&repo)?;
         let files = distate.tracked_files()?;
-        display_files(ui, &repo, files)
+        display_files(invocation.ui, &repo, files)
     }
 }
 

--- a/rust/rhg/src/commands/root.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/commands/root.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,11 +1,7 @@
 use crate::error::CommandError;
-use crate::ui::Ui;
-use clap::ArgMatches;
 use format_bytes::format_bytes;
-use hg::config::Config;
 use hg::repo::Repo;
 use hg::utils::files::get_bytes_from_path;
-use std::path::Path;
 
 pub const HELP_TEXT: &str = "
 Print the root directory of the current repository.
@@ -17,14 +13,11 @@
     clap::SubCommand::with_name("root").about(HELP_TEXT)
 }
 
-pub fn run(
-    ui: &Ui,
-    config: &Config,
-    repo_path: Option<&Path>,
-    _args: &ArgMatches,
-) -> Result<(), CommandError> {
-    let repo = Repo::find(config, repo_path)?;
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let repo = Repo::find(invocation.non_repo_config, invocation.repo_path)?;
     let bytes = get_bytes_from_path(repo.working_directory_path());
-    ui.write_stdout(&format_bytes!(b"{}\n", bytes.as_slice()))?;
+    invocation
+        .ui
+        .write_stdout(&format_bytes!(b"{}\n", bytes.as_slice()))?;
     Ok(())
 }

--- a/rust/rhg/src/main.rs	Fri Feb 12 16:54:30 2021 +0100
+++ b/rust/rhg/src/main.rs	Mon Feb 15 20:05:32 2021 +0100
@@ -1,9 +1,11 @@
 extern crate log;
+use crate::ui::Ui;
 use clap::App;
 use clap::AppSettings;
 use clap::Arg;
 use clap::ArgMatches;
 use format_bytes::format_bytes;
+use hg::config::Config;
 use std::path::Path;
 
 mod error;
@@ -48,31 +50,41 @@
     let (subcommand_name, subcommand_matches) = matches.subcommand();
     let run = subcommand_run_fn(subcommand_name)
         .expect("unknown subcommand name from clap despite AppSettings::SubcommandRequired");
-    let args = subcommand_matches
+    let subcommand_args = subcommand_matches
         .expect("no subcommand arguments from clap despite AppSettings::SubcommandRequired");
 
     // Global arguments can be in either based on e.g. `hg -R ./foo log` v.s.
     // `hg log -R ./foo`
-    let value_of_global_arg =
-        |name| args.value_of_os(name).or_else(|| matches.value_of_os(name));
+    let value_of_global_arg = |name| {
+        subcommand_args
+            .value_of_os(name)
+            .or_else(|| matches.value_of_os(name))
+    };
     // For arguments where multiple occurences are allowed, return a
     // possibly-iterator of all values.
     let values_of_global_arg = |name: &str| {
         let a = matches.values_of_os(name).into_iter().flatten();
-        let b = args.values_of_os(name).into_iter().flatten();
+        let b = subcommand_args.values_of_os(name).into_iter().flatten();
         a.chain(b)
     };
 
-    let repo_path = value_of_global_arg("repository").map(Path::new);
     let config_args = values_of_global_arg("config")
         // `get_bytes_from_path` works for OsStr the same as for Path
         .map(hg::utils::files::get_bytes_from_path);
-    let config = hg::config::Config::load(config_args)?;
-    run(&ui, &config, repo_path, args)
+    let non_repo_config = &hg::config::Config::load(config_args)?;
+
+    let repo_path = value_of_global_arg("repository").map(Path::new);
+
+    run(&CliInvocation {
+        ui,
+        subcommand_args,
+        non_repo_config,
+        repo_path,
+    })
 }
 
 fn main() {
-    let ui = ui::Ui::new();
+    let ui = Ui::new();
 
     let exit_code = match main_with_result(&ui) {
         Ok(()) => exitcode::OK,
@@ -109,12 +121,9 @@
             )+
         }
 
-        fn subcommand_run_fn(name: &str) -> Option<fn(
-            &ui::Ui,
-            &hg::config::Config,
-            Option<&Path>,
-            &ArgMatches,
-        ) -> Result<(), CommandError>> {
+        pub type RunFn = fn(&CliInvocation) -> Result<(), CommandError>;
+
+        fn subcommand_run_fn(name: &str) -> Option<RunFn> {
             match name {
                 $(
                     stringify!($command) => Some(commands::$command::run),
@@ -133,3 +142,9 @@
     root
     config
 }
+pub struct CliInvocation<'a> {
+    ui: &'a Ui,
+    subcommand_args: &'a ArgMatches<'a>,
+    non_repo_config: &'a Config,
+    repo_path: Option<&'a Path>,
+}