rust/hg-core/src/operations/mod.rs

rust: replace most "operation" structs with functions

The hg-core crate has a partially-formed concept of "operation",
represented as structs with constructors and a `run` method.

Each struct’s contructor takes different parameters,
and each `run` has a different return type.
Constructors typically don’t do much more than store parameters
for `run` to access them.

There was a comment about adding an `Operation` trait
when the language supports expressing something so general,
but it’s hard to imagine how operations with such different APIs
could be used in a generic context.

This commit starts removing the concept of "operation",
since those are pretty much just functions.

Differential Revision: https://phab.mercurial-scm.org/D9595

//! A distinction is made between operations and commands.
//! An operation is what can be done whereas a command is what is exposed by
//! the cli. A single command can use several operations to achieve its goal.

mod cat;
mod debugdata;
mod dirstate_status;
mod find_root;
mod list_tracked_files;
pub use cat::{cat, CatRevError, CatRevErrorKind};
pub use debugdata::{
    debug_data, DebugDataError, DebugDataErrorKind, DebugDataKind,
};
pub use find_root::{
    find_root, find_root_from_path, FindRootError, FindRootErrorKind,
};
pub use list_tracked_files::{
    list_rev_tracked_files, FilesForRev, ListRevTrackedFilesError,
    ListRevTrackedFilesErrorKind,
};
pub use list_tracked_files::{
    Dirstate, ListDirstateTrackedFilesError, ListDirstateTrackedFilesErrorKind,
};