install: add --only-dependencies option

The traditional approach to installing the dependencies of a formula is
the following:

  brew install `brew deps formula`

This approach ignores any options that are specified in the parent
formula. This pull request adds a --only-dependencies option to brew
install that installs the dependencies of a formula with optional flags,
but returns before installing the parent formula.

Closes Homebrew/homebrew#25272.

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

Library/Contributions/brew_bash_completion.sh

@@ -235,6 +235,7 @@ _brew_install ()
                 --HEAD
                 --ignore-dependencies
                 --interactive
+                --only-dependencies
                 --verbose
                 $(brew options --compact "$prv" 2>/dev/null)
                 "

Library/Contributions/manpages/brew.1.md

@@ -151,7 +151,7 @@ Note that these flags should only appear after a command.
   * `info` <URL>:
     Print the name and version that will be detected for <URL>.
 
-  * `install [--debug] [--env=<std|super>] [--ignore-dependencies] [--fresh] [--cc=<compiler>] [--build-from-source] [--devel|--HEAD]` <formula>:
+  * `install [--debug] [--env=<std|super>] [--ignore-dependencies] [--only-dependencies] [--fresh] [--cc=<compiler>] [--build-from-source] [--devel|--HEAD]` <formula>:
     Install <formula>.
 
     <formula> is usually the name of the formula to install, but it can be specified
@@ -170,6 +170,9 @@ Note that these flags should only appear after a command.
     any kind. If they are not already present, the formula will probably fail
     to install.
 
+    If `--only-dependencies` is passed, install the dependencies with specified
+    options but do not install the specified formula.
+
     If `--fresh` is passed, the installation process will not re-use any
     options from previous installs.
 

Library/Homebrew/extend/ARGV.rb

@@ -102,6 +102,10 @@ module HomebrewArgvExtension
     include? '--ignore-dependencies'
   end
 
+  def only_deps?
+    include? '--only-dependencies'
+  end
+
   def json
     value 'json'
   end

Library/Homebrew/formula_installer.rb

@@ -15,13 +15,14 @@ class FormulaInstaller
   include FormulaCellarChecks
 
   attr_reader :f
-  attr_accessor :tab, :options, :ignore_deps
+  attr_accessor :tab, :options, :ignore_deps, :only_deps
   attr_accessor :show_summary_heading, :show_header
 
   def initialize ff
     @f = ff
     @show_header = false
     @ignore_deps = ARGV.ignore_deps? || ARGV.interactive?
+    @only_deps = ARGV.only_deps?
     @options = Options.new
     @tab = Tab.dummy_tab(ff)
 
@@ -105,6 +106,8 @@ class FormulaInstaller
 
     compute_and_install_dependencies unless ignore_deps
 
+    return if only_deps
+
     if ARGV.build_bottle? && (arch = ARGV.bottle_arch) && !Hardware::CPU.optimization_flags.include?(arch)
       raise "Unrecognized architecture for --bottle-arch: #{arch}"
     end
@@ -270,6 +273,7 @@ class FormulaInstaller
     fi.tab = dep_tab
     fi.options = dep_options
     fi.ignore_deps = true
+    fi.only_deps = false
     fi.show_header = false
     oh1 "Installing #{f} dependency: #{Tty.green}#{dep}#{Tty.reset}"
     outdated_keg.unlink if outdated_keg
@@ -282,6 +286,8 @@ class FormulaInstaller
   end
 
   def caveats
+    return if only_deps
+
     if ARGV.homebrew_developer? and not f.keg_only?
       audit_bin
       audit_sbin
@@ -299,6 +305,8 @@ class FormulaInstaller
   end
 
   def finish
+    return if only_deps
+
     ohai 'Finishing up' if ARGV.verbose?
 
     install_plist

share/man/man1/brew.1

@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW" "1" "November 2013" "Homebrew" "brew"
+.TH "BREW" "1" "December 2013" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for OS X
@@ -174,7 +174,7 @@ To view formula history locally: \fBbrew log \-p <formula>\fR\.
 Print the name and version that will be detected for \fIURL\fR\.
 .
 .TP
-\fBinstall [\-\-debug] [\-\-env=<std|super>] [\-\-ignore\-dependencies] [\-\-fresh] [\-\-cc=<compiler>] [\-\-build\-from\-source] [\-\-devel|\-\-HEAD]\fR \fIformula\fR
+\fBinstall [\-\-debug] [\-\-env=<std|super>] [\-\-ignore\-dependencies] [\-\-only\-dependencies] [\-\-fresh] [\-\-cc=<compiler>] [\-\-build\-from\-source] [\-\-devel|\-\-HEAD]\fR \fIformula\fR
 Install \fIformula\fR\.
 .
 .IP
@@ -193,6 +193,9 @@ If \fB\-\-env=super\fR is passed, use superenv even if the formula specifies the
 If \fB\-\-ignore\-dependencies\fR is passed, skip installing any dependencies of any kind\. If they are not already present, the formula will probably fail to install\.
 .
 .IP
+If \fB\-\-only\-dependencies\fR is passed, install the dependencies with specified options but do not install the specified formula\.
+.
+.IP
 If \fB\-\-fresh\fR is passed, the installation process will not re\-use any options from previous installs\.
 .
 .IP