docs: Mention more shell functions in stdenv

doc/stdenv/stdenv.chapter.md

@@ -1223,10 +1223,19 @@ Example removing all references to the compiler in the output:
 
 ### `runHook` \<hook\> {#fun-runHook}
 
-Execute \<hook\> and the values in the array associated with it. The array's name is determined by removing `Hook` from the end of \<hook\> and appending `Hooks`.
+Execute \<hook\> and the values in the array associated with it. The array's name is determined by removing `Hook` from the end of \<hook\> and appending `Hooks`. Execution aborts on the first failing hook.
 
 For example, `runHook postHook` would run the hook `postHook` and all of the values contained in the `postHooks` array, if it exists.
 
+### `runOneHook` \<hook\> {#fun-runOneHook}
+
+Run all hooks that `runHook` would, but exit after the first successful hook.
+Failing hooks are ignored.
+
+### `echoCmd` \<cmd\> \<args...\> {#fun-echoCmd}
+
+Print (but don't execute) a command and unambiguously mark word splits.
+
 ### `substitute` \<infile\> \<outfile\> \<subs\> {#fun-substitute}
 
 Performs string substitution on the contents of \<infile\>, writing the result to \<outfile\>. The substitutions in \<subs\> are of the following form:

pkgs/stdenv/generic/setup.sh

@@ -200,6 +200,11 @@ _logHook() {
 # were added, stopping if any fails (returns a non-zero exit
 # code). The hooks for <hookName> are the shell function or variable
 # <hookName>, and the values of the shell array ‘<hookName>Hooks’.
+#
+# Documented in:
+# - source: `doc/stdenv/stdenv.chapter.md`
+# - stable docs: https://nixos.org/manual/nixpkgs/stable/#fun-runHook
+# - unstable docs: https://nixos.org/manual/nixpkgs/unstable/#fun-runHook
 runHook() {
     local hookName="$1"
     shift
@@ -219,6 +224,11 @@ runHook() {
 
 # Run all hooks with the specified name, until one succeeds (returns a
 # zero exit code). If none succeed, return a non-zero exit code.
+#
+# Documented in:
+# - source: `doc/stdenv/stdenv.chapter.md`
+# - stable docs: https://nixos.org/manual/nixpkgs/stable/#fun-runOneHook
+# - unstable docs: https://nixos.org/manual/nixpkgs/unstable/#fun-runOneHook
 runOneHook() {
     local hookName="$1"
     shift
@@ -283,6 +293,11 @@ _eval() {
 # to split the command in three parts because the middle format string
 # will be, and must be, repeated for each argument. The first argument
 # goes before the ':' and is just for convenience.
+#
+# Documented in:
+# - source: `doc/stdenv/stdenv.chapter.md`
+# - stable docs: https://nixos.org/manual/nixpkgs/stable/#fun-echoCmd
+# - unstable docs: https://nixos.org/manual/nixpkgs/unstable/#fun-echoCmd
 echoCmd() {
     printf "%s:" "$1"
     shift