rust/hg-cpython/src/dagops.rs

phabricator: combine commit messages into the review when folding commits

No visible changes here, until an option to enable it is added to `phabsend`.

This combines the Differential fields like Arcanist does, rather than simply
concatenating the text blocks.  Aside from populating everything properly in the
web interface, Phabricator fails the review create/update if repeated fields are
seen as would happen with simple concatenation.

On the flip side, now that the Summary and Test Plan fields can contain data
from multiple commits, we can't just join these fields together to determine if
an amend is needed.  If that were to happen, every single commit in the folded
range would get amended with the combined commit message, which seems clearly
wrong.  Aside from making a minor assumption about the content of the
Differential Revision field (it seems they allow some minor variances with
spacing), this means that for folded reviews, you can't post it, go to the web
page add a missing Test Plan, and then get it added to the commit message by
re-posting it.  I don't think that's a big deal.

Differential Revision: https://phab.mercurial-scm.org/D8309

// dagops.rs
//
// Copyright 2019 Georges Racinet <[e-mail]>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

//! Bindings for the `hg::dagops` module provided by the
//! `hg-core` package.
//!
//! From Python, this will be seen as `mercurial.rustext.dagop`
use crate::{conversion::rev_pyiter_collect, exceptions::GraphError};
use cpython::{PyDict, PyModule, PyObject, PyResult, Python};
use hg::dagops;
use hg::Revision;
use std::collections::HashSet;

use crate::revlog::pyindex_to_graph;

/// Using the the `index`, return heads out of any Python iterable of Revisions
///
/// This is the Rust counterpart for `mercurial.dagop.headrevs`
pub fn headrevs(
    py: Python,
    index: PyObject,
    revs: PyObject,
) -> PyResult<HashSet<Revision>> {
    let mut as_set: HashSet<Revision> = rev_pyiter_collect(py, &revs)?;
    dagops::retain_heads(&pyindex_to_graph(py, index)?, &mut as_set)
        .map_err(|e| GraphError::pynew(py, e))?;
    Ok(as_set)
}

/// Create the module, with `__package__` given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.dagop", package);
    let m = PyModule::new(py, dotted_name)?;
    m.add(py, "__package__", package)?;
    m.add(py, "__doc__", "DAG operations - Rust implementation")?;
    m.add(
        py,
        "headrevs",
        py_fn!(py, headrevs(index: PyObject, revs: PyObject)),
    )?;

    let sys = PyModule::import(py, "sys")?;
    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
    sys_modules.set_item(py, dotted_name, &m)?;
    // Example C code (see pyexpat.c and import.c) will "give away the
    // reference", but we won't because it will be consumed once the
    // Rust PyObject is dropped.
    Ok(m)
}