completions: clarify that only external tap completions are affected

Co-Authored-By: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/cmd/completions.rb

@@ -15,7 +15,7 @@ module Homebrew
       usage_banner <<~EOS
         `completions` [<subcommand>]
 
-        Control whether Homebrew automatically links shell completion files.
+        Control whether Homebrew automatically links external tap shell completion files.
         Read more at <https://docs.brew.sh/Shell-Completion>.
 
         `brew completions` [`state`]:

Library/Homebrew/completions.rb

@@ -56,7 +56,7 @@ module Completions
 
     T.unsafe(self).ohai "Homebrew completions for external commands are unlinked by default!"
     T.unsafe(self).puts <<~EOS
-      To opt-in to automatically linking Homebrew shell competion files, run:
+      To opt-in to automatically linking external tap shell competion files, run:
         brew completions link
       Then, follow the directions at #{Formatter.url("https://docs.brew.sh/Shell-Completion")}
     EOS

docs/Manpage.md

@@ -96,7 +96,7 @@ Show lists of built-in and external commands.
 
 ### `completions` [*`subcommand`*]
 
-Control whether Homebrew automatically links shell completion files.
+Control whether Homebrew automatically links external tap shell completion files.
 Read more at <https://docs.brew.sh/Shell-Completion>.
 
 `brew completions` [`state`]

manpages/brew.1

@@ -94,7 +94,7 @@ List only the names of commands without category headers\.
 Include aliases of internal commands\.
 .
 .SS "\fBcompletions\fR [\fIsubcommand\fR]"
-Control whether Homebrew automatically links shell completion files\. Read more at \fIhttps://docs\.brew\.sh/Shell\-Completion\fR\.
+Control whether Homebrew automatically links external tap shell completion files\. Read more at \fIhttps://docs\.brew\.sh/Shell\-Completion\fR\.
 .
 .P
 \fBbrew completions\fR [\fBstate\fR]