docs: use proper rst markup for preformatted blocks

The multiple lines were re-flowed to a single line, both in man page and html.

mercurial/helptext/rust.txt

@@ -1,95 +1,96 b''
 Mercurial can be augmented with Rust extensions for speeding up certain
 operations.
 
 Compatibility
 =============
 
 Though the Rust extensions are only tested by the project under Linux, users of
 MacOS, FreeBSD and other UNIX-likes have been using the Rust extensions. Your
 mileage may vary, but by all means do give us feedback or signal your interest
 for better support.
 
 No Rust extensions are available for Windows at this time.
 
 Features
 ========
 
 The following operations are sped up when using Rust:
 
     - discovery of differences between repositories (pull/push)
     - nodemap (see :hg:`help config.format.use-persistent-nodemap`)
     - all commands using the dirstate (status, commit, diff, add, update, etc.)
     - dirstate-v2 (see :hg:`help config.format.use-dirstate-v2`)
     - iteration over ancestors in a graph
 
 More features are in the works, and improvements on the above listed are still
 in progress. For more experimental work see the "rhg" section.
 
 Checking for Rust
 =================
 
-You may already have the Rust extensions depending on how you install Mercurial.
+You may already have the Rust extensions depending on how you install
+Mercurial::
 
   $ hg debuginstall | grep -i rust
   checking Rust extensions (installed)
   checking module policy (rust+c-allow)
 
 If those lines don't even exist, you're using an old version of `hg` which does
 not have any Rust extensions yet.
 
 Installing
 ==========
 
 You will need `cargo` to be in your `$PATH`. See the "MSRV" section for which
 version to use.
 
 Using pip
 ---------
 
-Users of `pip` can install the Rust extensions with the following command:
+Users of `pip` can install the Rust extensions with the following command::
 
   $ pip install mercurial --global-option --rust --no-use-pep517
 
 `--no-use-pep517` is here to tell `pip` to preserve backwards compatibility with
 the legacy `setup.py` system. Mercurial has not yet migrated its complex setup
 to the new system, so we still need this to add compiled extensions.
 
 This might take a couple of minutes because you're compiling everything.
 
 See the "Checking for Rust" section to see if the install succeeded.
 
 From your distribution
 ----------------------
 
 Some distributions are shipping Mercurial with Rust extensions enabled and
 pre-compiled (meaning you won't have to install `cargo`), or allow you to
 specify an install flag. Check with your specific distribution for how to do
 that, or ask their team to add support for hg+Rust!
 
 From source
 -----------
 
 Please refer to the `rust/README.rst` file in the Mercurial repository for
 instructions on how to install from source.
 
 MSRV
 ====
 
 The minimum supported Rust version is currently 1.48.0. The project's policy is
 to follow the version from Debian stable, to make the distributions' job easier.
 
 rhg
 ===
 
 There exists an experimental pure-Rust version of Mercurial called `rhg` with a
 fallback mechanism for unsupported invocations. It allows for much faster
 execution of certain commands while adding no discernable overhead for the rest.
 
 The only way of trying it out is by building it from source. Please refer to
 `rust/README.rst` in the Mercurial repository.
 
 Contributing
 ============
 
 If you would like to help the Rust endeavor, please refer to `rust/README.rst`
 in the Mercurial repository.