trivial-builders: Deduplicate docs

I didn't have the opportunity to do all work at once, so I've added
TODOs to bring attention to the situation.

2 files changed, 13 insertions, 1 deletions

diff --git a/doc/build-helpers/fetchers.chapter.md b/doc/build-helpers/fetchers.chapter.md
index ad2378fd0e74..b326f189d50e 100644
--- a/doc/build-helpers/fetchers.chapter.md
+++ b/doc/build-helpers/fetchers.chapter.md
@@ -262,6 +262,10 @@ or
 
 ***
 ```
+
+This function should only be used by non-redistributable software with an unfree license that we need to require the user to download manually.
+It produces packages that cannot be built automatically.
+
 ## `fetchtorrent` {#fetchtorrent}
 
 `fetchtorrent` expects two arguments. `url` which can either be a Magnet URI (Magnet Link) such as `magnet:?xt=urn:btih:dd8255ecdc7ca55fb0bbf81323d87062db1f6d1c` or an HTTP URL pointing to a `.torrent` file. It can also take a `config` argument which will craft a `settings.json` configuration file and give it to `transmission`, the underlying program that is performing the fetch. The available config options for `transmission` can be found [here](https://github.com/transmission/transmission/blob/main/docs/Editing-Configuration-Files.md#options)
diff --git a/doc/build-helpers/trivial-build-helpers.chapter.md b/doc/build-helpers/trivial-build-helpers.chapter.md
index 384e25035060..02d0a8682bf7 100644
--- a/doc/build-helpers/trivial-build-helpers.chapter.md
+++ b/doc/build-helpers/trivial-build-helpers.chapter.md
@@ -7,7 +7,9 @@ Like [`stdenv.mkDerivation`](#sec-using-stdenv), each of these build helpers cre
 
 `runCommand :: String -> AttrSet -> String -> Derivation`
 
-`runCommand name drvAttrs buildCommand` returns a derivation that is built by running the specified shell commands.
+The result of `runCommand name drvAttrs buildCommand` is a derivation that is built by running the specified shell commands.
+
+By default `runCommand` runs in a stdenv with no compiler environment, whereas [`runCommandCC`](#trivial-builder-runCommandCC) uses the default stdenv, `pkgs.stdenv`.
 
 `name :: String`
 :   The name that Nix will append to the store path in the same way that `stdenv.mkDerivation` uses its `name` attribute.
@@ -153,6 +155,12 @@ Write a text file to the Nix store.
 
   Default: `true`
 
+`derivationArgs` (Attribute set, _optional_)
+
+: Extra arguments to pass to the underlying call to `stdenv.mkDerivation`.
+
+  Default: `{}`
+
 The resulting store path will include some variation of the name, and it will be a file unless `destination` is used, in which case it will be a directory.
 
 ::: {.example #ex-writeTextFile}