doc: prepare for commonmark

We are still using Pandoc’s Markdown parser, which differs from CommonMark spec slightly.

Notably:
- Line breaks in lists behave differently.
- Admonitions do not support the simpler syntax https://github.com/jgm/commonmark-hs/issues/75
- The auto_identifiers uses a different algorithm – I made the previous ones explicit.
- Languages (classes) of code blocks cannot contain whitespace so we have to use “pycon” alias instead of Python “console” as GitHub’s linguist

While at it, I also fixed the following issues:
- ShellSesssion was used
- Removed some pointless docbook tags.

1 files changed, 1 insertions, 1 deletions

diff --git a/doc/using/overlays.chapter.md b/doc/using/overlays.chapter.md
index 21efe467b847..537d031bcdb3 100644
--- a/doc/using/overlays.chapter.md
+++ b/doc/using/overlays.chapter.md
@@ -63,7 +63,7 @@ The second argument (`super`) corresponds to the result of the evaluation of the
 
 The value returned by this function should be a set similar to `pkgs/top-level/all-packages.nix`, containing overridden and/or new packages.
 
-Overlays are similar to other methods for customizing Nixpkgs, in particular the `packageOverrides` attribute described in <xref linkend="sec-modify-via-packageOverrides"/>. Indeed, `packageOverrides` acts as an overlay with only the `super` argument. It is therefore appropriate for basic use, but overlays are more powerful and easier to distribute.
+Overlays are similar to other methods for customizing Nixpkgs, in particular the `packageOverrides` attribute described in<xref linkend="sec-modify-via-packageOverrides"/>. Indeed, `packageOverrides` acts as an overlay with only the `super` argument. It is therefore appropriate for basic use, but overlays are more powerful and easier to distribute.
 
 ## Using overlays to configure alternatives {#sec-overlays-alternatives}