rhg: refactor function to relativize paths in utils

rhg: refactor function to relativize paths in utils

Commands like `files`, `status` supports printing relative paths. Hence we need
to re-use this code in other places too. So let's take this out from `rhg files`
into a utility function.

Next patch will make `rhg status` use it.

Differential Revision: https://phab.mercurial-scm.org/D11613

--- a/rust/rhg/src/commands/files.rs	Wed Oct 06 13:32:07 2021 +0530
+++ b/rust/rhg/src/commands/files.rs	Tue Oct 05 18:02:22 2021 +0530
@@ -1,12 +1,13 @@
 use crate::error::CommandError;
 use crate::ui::Ui;
+use crate::ui::UiError;
+use crate::utils::path_utils::relativize_paths;
 use clap::Arg;
 use hg::operations::list_rev_tracked_files;
 use hg::operations::Dirstate;
 use hg::repo::Repo;
-use hg::utils::current_dir;
-use hg::utils::files::{get_bytes_from_path, relativize_path};
-use hg::utils::hg_path::{HgPath, HgPathBuf};
+use hg::utils::hg_path::HgPath;
+use std::borrow::Cow;
 
 pub const HELP_TEXT: &str = "
 List tracked files.
@@ -54,34 +55,13 @@
     files: impl IntoIterator<Item = &'a HgPath>,
 ) -> Result<(), CommandError> {
     let mut stdout = ui.stdout_buffer();
-
-    let cwd = current_dir()?;
-    let working_directory = repo.working_directory_path();
-    let working_directory = cwd.join(working_directory); // Make it absolute
+    let mut any = false;
 
-    let mut any = false;
-    if let Ok(cwd_relative_to_repo) = cwd.strip_prefix(&working_directory) {
-        // The current directory is inside the repo, so we can work with
-        // relative paths
-        let cwd = HgPathBuf::from(get_bytes_from_path(cwd_relative_to_repo));
-        for file in files {
-            any = true;
-            stdout.write_all(relativize_path(&file, &cwd).as_ref())?;
-            stdout.write_all(b"\n")?;
-        }
-    } else {
-        let working_directory =
-            HgPathBuf::from(get_bytes_from_path(working_directory));
-        let cwd = HgPathBuf::from(get_bytes_from_path(cwd));
-        for file in files {
-            any = true;
-            // Absolute path in the filesystem
-            let file = working_directory.join(file);
-            stdout.write_all(relativize_path(&file, &cwd).as_ref())?;
-            stdout.write_all(b"\n")?;
-        }
-    }
-
+    relativize_paths(repo, files, |path: Cow<[u8]>| -> Result<(), UiError> {
+        any = true;
+        stdout.write_all(path.as_ref())?;
+        stdout.write_all(b"\n")
+    })?;
     stdout.flush()?;
     if any {
         Ok(())

--- a/rust/rhg/src/main.rs	Wed Oct 06 13:32:07 2021 +0530
+++ b/rust/rhg/src/main.rs	Tue Oct 05 18:02:22 2021 +0530
@@ -17,6 +17,9 @@
 mod blackbox;
 mod error;
 mod ui;
+pub mod utils {
+    pub mod path_utils;
+}
 use error::CommandError;
 
 fn main_with_result(

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/rhg/src/utils/path_utils.rs	Tue Oct 05 18:02:22 2021 +0530
@@ -0,0 +1,48 @@
+// path utils module
+//
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2 or any later version.
+
+use crate::error::CommandError;
+use crate::ui::UiError;
+use hg::repo::Repo;
+use hg::utils::current_dir;
+use hg::utils::files::{get_bytes_from_path, relativize_path};
+use hg::utils::hg_path::HgPath;
+use hg::utils::hg_path::HgPathBuf;
+use std::borrow::Cow;
+
+pub fn relativize_paths(
+    repo: &Repo,
+    paths: impl IntoIterator<Item = impl AsRef<HgPath>>,
+    mut callback: impl FnMut(Cow<[u8]>) -> Result<(), UiError>,
+) -> Result<(), CommandError> {
+    let cwd = current_dir()?;
+    let repo_root = repo.working_directory_path();
+    let repo_root = cwd.join(repo_root); // Make it absolute
+    let repo_root_hgpath =
+        HgPathBuf::from(get_bytes_from_path(repo_root.to_owned()));
+    let outside_repo: bool;
+    let cwd_hgpath: HgPathBuf;
+
+    if let Ok(cwd_relative_to_repo) = cwd.strip_prefix(&repo_root) {
+        // The current directory is inside the repo, so we can work with
+        // relative paths
+        outside_repo = false;
+        cwd_hgpath =
+            HgPathBuf::from(get_bytes_from_path(cwd_relative_to_repo));
+    } else {
+        outside_repo = true;
+        cwd_hgpath = HgPathBuf::from(get_bytes_from_path(cwd));
+    }
+
+    for file in paths {
+        if outside_repo {
+            let file = repo_root_hgpath.join(file.as_ref());
+            callback(relativize_path(&file, &cwd_hgpath))?;
+        } else {
+            callback(relativize_path(file.as_ref(), &cwd_hgpath))?;
+        }
+    }
+    Ok(())
+}