rhg: add a `Files` `Command` to prepare the `rhg files` subcommand

rhg: add a `Files` `Command` to prepare the `rhg files` subcommand

Differential Revision: https://phab.mercurial-scm.org/D8868

--- a/rust/hg-core/src/lib.rs	Wed Jul 29 15:49:44 2020 +0200
+++ b/rust/hg-core/src/lib.rs	Wed Jul 29 10:21:17 2020 +0200
@@ -57,6 +57,7 @@
 pub enum DirstateParseError {
     TooLittleData,
     Overflow,
+    // TODO refactor to use bytes instead of String
     CorruptedEntry(String),
     Damaged,
 }

--- a/rust/rhg/src/commands.rs	Wed Jul 29 15:49:44 2020 +0200
+++ b/rust/rhg/src/commands.rs	Wed Jul 29 10:21:17 2020 +0200
@@ -1,3 +1,4 @@
+pub mod files;
 pub mod root;
 use crate::error::CommandError;
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/rhg/src/commands/files.rs	Wed Jul 29 10:21:17 2020 +0200
@@ -0,0 +1,50 @@
+use crate::commands::Command;
+use crate::error::{CommandError, CommandErrorKind};
+use crate::ui::Ui;
+use hg::operations::{ListTrackedFiles, ListTrackedFilesErrorKind};
+
+pub const HELP_TEXT: &str = "
+List tracked files.
+
+Returns 0 on success.
+";
+
+pub struct FilesCommand<'a> {
+    ui: &'a Ui,
+}
+
+impl<'a> FilesCommand<'a> {
+    pub fn new(ui: &'a Ui) -> Self {
+        FilesCommand { ui }
+    }
+}
+
+impl<'a> Command<'a> for FilesCommand<'a> {
+    fn run(&self) -> Result<(), CommandError> {
+        let operation_builder = ListTrackedFiles::new()?;
+        let operation = operation_builder.load().map_err(|err| {
+            CommandErrorKind::Abort(Some(
+                [b"abort: ", err.to_string().as_bytes(), b"\n"]
+                    .concat()
+                    .to_vec(),
+            ))
+        })?;
+        let files = operation.run().map_err(|err| match err.kind {
+            ListTrackedFilesErrorKind::ParseError(_) => {
+                CommandErrorKind::Abort(Some(
+                    // TODO find a better error message
+                    b"abort: parse error\n".to_vec(),
+                ))
+            }
+        })?;
+
+        let mut stdout = self.ui.stdout_buffer();
+        for file in files {
+            stdout.write_all(file.as_bytes())?;
+            stdout.write_all(b"\n")?;
+        }
+        stdout.flush()?;
+
+        Ok(())
+    }
+}

--- a/rust/rhg/src/error.rs	Wed Jul 29 15:49:44 2020 +0200
+++ b/rust/rhg/src/error.rs	Wed Jul 29 10:21:17 2020 +0200
@@ -16,6 +16,8 @@
     StdoutError,
     /// The standard error stream cannot be written to
     StderrError,
+    /// The command aborted
+    Abort(Option<Vec<u8>>),
 }
 
 impl CommandErrorKind {
@@ -25,6 +27,7 @@
             CommandErrorKind::CurrentDirNotFound(_) => exitcode::ABORT,
             CommandErrorKind::StdoutError => exitcode::ABORT,
             CommandErrorKind::StderrError => exitcode::ABORT,
+            CommandErrorKind::Abort(_) => exitcode::ABORT,
         }
     }
 
@@ -52,6 +55,7 @@
                 ]
                 .concat(),
             ),
+            CommandErrorKind::Abort(message) => message.to_owned(),
             _ => None,
         }
     }