--repository: support to show tap path

This can become handy when we separate core code and formulae. For
example, we could use `cd $(brew --repo homebrew/core)` to go to core
tap path.

Closes Homebrew/homebrew#50346.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/cmd/--repository.rb

@@ -1,5 +1,11 @@
+require "tap"
+
 module Homebrew
   def __repository
+    if ARGV.named.empty?
       puts HOMEBREW_REPOSITORY
+    else
+      puts ARGV.named.map { |tap| Tap.fetch(tap).path }
+    end
   end
 end

Library/Homebrew/manpages/brew.1.md

@@ -529,6 +529,9 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     Display where Homebrew's `.git` directory is located. For standard installs,
     the `prefix` and `repository` are the same directory.
 
+  * `--repository` <user>`/`<repo>:
+    Display where tap <user>`/`<repo>'s directory is located.
+
   * `--version`:
     Print the version number of brew to standard error and exit.
 

Library/Homebrew/test/test_integration_cmds.rb

@@ -124,6 +124,11 @@ class IntegrationCommandTests < Homebrew::TestCase
                  cmd("--repository")
   end
 
+  def test_repository
+    assert_match "#{HOMEBREW_LIBRARY}/Taps/foo/homebrew-bar",
+                 cmd("--repository", "foo/bar")
+  end
+
   def test_help
     assert_match "Example usage:",
                  cmd("help")

share/doc/homebrew/brew.1.html

@@ -389,6 +389,7 @@ without any sort of versioned directory as the last path.</p></dd>
 <dt><code>--prefix</code> <var>formula</var></dt><dd><p>Display the location in the cellar where <var>formula</var> is or would be installed.</p></dd>
 <dt><code>--repository</code></dt><dd><p>Display where Homebrew's <code>.git</code> directory is located. For standard installs,
 the <code>prefix</code> and <code>repository</code> are the same directory.</p></dd>
+<dt><code>--repository</code> <var>user</var><code>/</code><var>repo</var></dt><dd><p>Display where tap <var>user</var><code>/</code><var>repo</var>'s directory is located.</p></dd>
 <dt><code>--version</code></dt><dd><p>Print the version number of brew to standard error and exit.</p></dd>
 </dl>
 

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" "January 2016" "Homebrew" "brew"
+.TH "BREW" "1" "March 2016" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for OS X
@@ -566,6 +566,10 @@ Display the location in the cellar where \fIformula\fR is or would be installed\
 Display where Homebrew\'s \fB\.git\fR directory is located\. For standard installs, the \fBprefix\fR and \fBrepository\fR are the same directory\.
 .
 .TP
+\fB\-\-repository\fR \fIuser\fR\fB/\fR\fIrepo\fR
+Display where tap \fIuser\fR\fB/\fR\fIrepo\fR\'s directory is located\.
+.
+.TP
 \fB\-\-version\fR
 Print the version number of brew to standard error and exit\.
 .