rust-hg-cpython: add an `HgProgressBar` util

This will be the entry point for all progress bars from a Python context
in upcoming patches. Like the `Progress` trait, this is subject to change
once we have more use cases, but this is good enough for now.

rust/Cargo.lock

@@ -231,6 +231,19 dependencies = [
 ]
 
 [[package]]
+name = "console"
+version = "0.15.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e1f83fc076bd6dd27517eacdf25fef6c4dfe5f1d7448bafaaf3a26f13b5e4eb"
+dependencies = [
+ "encode_unicode",
+ "lazy_static",
+ "libc",
+ "unicode-width",
+ "windows-sys 0.52.0",
+]
+
+[[package]]
 name = "convert_case"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -451,6 +464,12 source = "registry+https://github.com/ru
 checksum = "90e5c1c8368803113bf0c9584fc495a58b86dc8a29edbf8fe877d21d9507e797"
 
 [[package]]
+name = "encode_unicode"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a357d28ed41a50f9c765dbfe56cbc04a64e53e5fc58ba79fbc34c10ef3df831f"
+
+[[package]]
 name = "env_logger"
 version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -609,6 +628,7 dependencies = [
  "hashbrown 0.13.1",
  "home",
  "im-rc",
+ "indicatif",
  "itertools",
  "lazy_static",
  "libc",
@@ -711,6 +731,19 dependencies = [
 ]
 
 [[package]]
+name = "indicatif"
+version = "0.17.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "763a5a8f45087d6bcea4222e7b72c291a054edf80e4ef6efd2a4979878c7bea3"
+dependencies = [
+ "console",
+ "instant",
+ "number_prefix",
+ "portable-atomic",
+ "unicode-width",
+]
+
+[[package]]
 name = "instant"
 version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -890,6 +923,12 dependencies = [
 ]
 
 [[package]]
+name = "number_prefix"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "830b246a0e5f20af87141b25c173cd1b609bd7779a4617d6ec582abaf90870f3"
+
+[[package]]
 name = "once_cell"
 version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -938,6 +977,12 source = "registry+https://github.com/ru
 checksum = "6ac9a59f73473f1b8d852421e59e64809f025994837ef743615c6d0c5b305160"
 
 [[package]]
+name = "portable-atomic"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc9c68a3f6da06753e9335d63e27f6b9754dd1920d941135b7ea8224f141adb2"
+
+[[package]]
 name = "ppv-lite86"
 version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1646,6 +1691,15 dependencies = [
 
 [[package]]
 name = "windows-sys"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "282be5f36a8ce781fad8c8ae18fa3f9beff57ec1b52cb3de0789201425d9a33d"
+dependencies = [
+ "windows-targets 0.52.6",
+]
+
+[[package]]
+name = "windows-sys"
 version = "0.59.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e38bc4d79ed67fd075bcc251a1c39b32a1776bbe92e5bef1f0bf1f8c531853b"

rust/hg-core/Cargo.toml

@@ -16,6 +16,7 derive_more = "0.99.17"
 hashbrown = { version = "0.13.1", features = ["rayon"] }
 home = "0.5.4"
 im-rc = "15.1.0"
+indicatif = "0.17.8"
 itertools = "0.10.5"
 lazy_static = "1.4.0"
 libc = "0.2.137"

rust/hg-core/src/progress.rs

@@ -1,5 +1,12
 //! Progress-bar related things
 
+use std::{
+    sync::atomic::{AtomicBool, Ordering},
+    time::Duration,
+};
+
+use indicatif::{ProgressBar, ProgressDrawTarget, ProgressStyle};
+
 /// A generic determinate progress bar trait
 pub trait Progress: Send + Sync + 'static {
     /// Set the current position and optionally the total
@@ -9,3 +16,77 pub trait Progress: Send + Sync + 'stati
     /// Declare that progress is over and the progress bar should be deleted
     fn complete(self);
 }
+
+const PROGRESS_DELAY: Duration = Duration::from_secs(1);
+
+/// A generic (determinate) progress bar. Stays hidden until [`PROGRESS_DELAY`]
+/// to prevent flickering a progress bar for super fast operations.
+pub struct HgProgressBar {
+    progress: ProgressBar,
+    has_been_shown: AtomicBool,
+}
+
+impl HgProgressBar {
+    // TODO pass config to check progress.disable/assume-tty/delay/etc.
+    /// Return a new progress bar with `topic` as the prefix.
+    /// The progress and total are both set to 0, and it is hidden until the
+    /// next call to `update` given that more than a second has elapsed.
+    pub fn new(topic: &str) -> Self {
+        let template =
+            format!("{} {{wide_bar}} {{pos}}/{{len}} {{eta}} ", topic);
+        let style = ProgressStyle::with_template(&template).unwrap();
+        let progress_bar = ProgressBar::new(0).with_style(style);
+        // Hide the progress bar and only show it if we've elapsed more
+        // than a second
+        progress_bar.set_draw_target(ProgressDrawTarget::hidden());
+        Self {
+            progress: progress_bar,
+            has_been_shown: false.into(),
+        }
+    }
+
+    /// Called whenever the progress changes to determine whether to start
+    /// showing the progress bar
+    fn maybe_show(&self) {
+        if self.progress.is_hidden()
+            && self.progress.elapsed() > PROGRESS_DELAY
+        {
+            // Catch a race condition whereby we check if it's hidden, then
+            // set the draw target from another thread, then do it again from
+            // this thread, which results in multiple progress bar lines being
+            // left drawn.
+            let has_been_shown =
+                self.has_been_shown.fetch_or(true, Ordering::Relaxed);
+            if !has_been_shown {
+                // Here we are certain that we're the only thread that has
+                // set `has_been_shown` and we can change the draw target
+                self.progress.set_draw_target(ProgressDrawTarget::stderr());
+                self.progress.tick();
+            }
+        }
+    }
+}
+
+impl Progress for HgProgressBar {
+    fn update(&self, pos: u64, total: Option<u64>) {
+        self.progress.update(|state| {
+            state.set_pos(pos);
+            if let Some(t) = total {
+                state.set_len(t)
+            }
+        });
+        self.maybe_show();
+    }
+
+    fn increment(&self, step: u64, total: Option<u64>) {
+        self.progress.inc(step);
+        if let Some(t) = total {
+            self.progress.set_length(t)
+        }
+        self.maybe_show();
+    }
+
+    fn complete(self) {
+        self.progress.finish_and_clear();
+    }
+}