brew-options: add --installed flag

`brew options --installed` will print options for formulae that are
already installed.

Closes Homebrew/homebrew#7565.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Contributions/manpages/brew.1.md

@@ -184,7 +184,7 @@ For the full command list, see the COMMANDS section.
 
     If no <formulae> are given, check all installed brews.
 
-  * `options [--compact] [--all]` <formula>:
+  * `options [--compact] [--all] [--installed]` <formula>:
     Display install options specific to <formula>.
 
     If `--compact` is passed, show all options on a single line separated by
@@ -192,6 +192,8 @@ For the full command list, see the COMMANDS section.
 
     If `--all` is passed, show options for all formulae.
 
+    If `--installed` is passed, show options for all installed formulae.
+
   * `outdated [--quiet]`:
     Show formulae that have an updated version available.
 

Library/Homebrew/cmd/options.rb

@@ -3,6 +3,8 @@ require 'formula'
 def ff
   if ARGV.include? "--all"
     Formula.all
+  elsif ARGV.include? "--installed"
+    Formula.all.reject{ |f| not f.installed? }
   else
     ARGV.formulae
   end

share/man/man1/brew.1

@@ -206,7 +206,7 @@ Check the given \fIformulae\fR for missing dependencies\.
 If no \fIformulae\fR are given, check all installed brews\.
 .
 .TP
-\fBoptions [\-\-compact] [\-\-all]\fR \fIformula\fR
+\fBoptions [\-\-compact] [\-\-all] [\-\-installed]\fR \fIformula\fR
 Display install options specific to \fIformula\fR\.
 .
 .IP
@@ -215,6 +215,9 @@ If \fB\-\-compact\fR is passed, show all options on a single line separated by s
 .IP
 If \fB\-\-all\fR is passed, show options for all formulae\.
 .
+.IP
+If \fB\-\-installed\fR is passed, show options for all installed formulae\.
+.
 .TP
 \fBoutdated [\-\-quiet]\fR
 Show formulae that have an updated version available\.