Add brew release-notes developer command.

Outputs the merged pull requests on Homebrew/brew between two Git refs.

Library/Homebrew/dev-cmd/release-notes.rb

@@ -0,0 +1,43 @@
+#:  * `release-notes` [<previous_tag>] [<end_ref>]:
+#:    Output the merged pull requests on Homebrew/brew between two Git refs.
+#:    If no `previous_tag` is provided it defaults to the newest tag.
+#:    If no `end_ref` is provided it defaults to `origin/master`.
+#:
+#:    If `--markdown` is passed, output as a Markdown list.
+
+module Homebrew
+  module_function
+
+  def release_notes
+    previous_tag = ARGV.named.first
+    unless previous_tag
+      previous_tag = Utils.popen_read("git tag --list --sort=-version:refname")
+                          .lines.first.chomp
+    end
+    odie "Could not find any previous tags!" unless previous_tag
+
+    end_ref = ARGV.named[1] || "origin/master"
+
+    [previous_tag, end_ref].each do |ref|
+      next if quiet_system "git", "rev-parse", "--verify", "--quiet", ref
+      odie "Ref #{ref} does not exist!"
+    end
+
+    output = Utils.popen_read("git log --pretty=format:'%s >> - %b%n' '#{previous_tag}'..'#{end_ref}'")
+                  .lines.grep(/Merge pull request/)
+
+    output.map! do |s|
+      s.gsub(/.*Merge pull request #(\d+)[^>]*(>>)*/,
+             "https://github.com/Homebrew/brew/pull/\\1")
+    end
+    if ARGV.include?("--markdown")
+      output.map! do |s|
+        /(.*\d)+ - (.*)/ =~ s
+        "- [#{$2}](#{$1})"
+      end
+    end
+
+    puts "Release notes between #{previous_tag} and #{end_ref}:"
+    puts output
+  end
+end

docs/brew.1.html

@@ -567,6 +567,11 @@ Each <patch-source> may be one of:
    If <code>--no-publish</code> was passed, do not publish bottles to Bintray.</p>
 
 <dl>
+<dt><code>release-notes</code> [<var>previous_tag</var>] [<var>end_ref</var>]</dt><dd><p>Output the merged pull requests on Homebrew/brew between two Git refs.
+If no <code>previous_tag</code> is provided it defaults to the newest tag.
+If no <code>end_ref</code> is provided it defaults to <code>origin/master</code>.</p>
+
+<p>If <code>--markdown</code> is passed, output as a Markdown list.</p></dd>
 <dt><code>tap-new</code> <var>user</var><code>/</code><var>repo</var></dt><dd><p>Generate the template files for a new tap.</p></dd>
 <dt><code>test</code> [<code>--devel</code>|<code>--HEAD</code>] [<code>--debug</code>] [<code>--keep-tmp</code>] <var>formula</var></dt><dd><p>Most formulae provide a test method. <code>brew test</code> <var>formula</var> runs this
 test method. There is no standard output or return code, but it should

manpages/brew.1

@@ -759,6 +759,13 @@ Each <patch\-source> may be one of:
 If \fB\-\-bottle\fR was passed, handle bottles, pulling the bottle\-update commit and publishing files on Bintray\. If \fB\-\-bump\fR was passed, for one\-formula PRs, automatically reword commit message to our preferred format\. If \fB\-\-clean\fR was passed, do not rewrite or otherwise modify the commits found in the pulled PR\. If \fB\-\-ignore\-whitespace\fR was passed, silently ignore whitespace discrepancies when applying diffs\. If \fB\-\-resolve\fR was passed, when a patch fails to apply, leave in progress and allow user to resolve, instead of aborting\. If \fB\-\-branch\-okay\fR was passed, do not warn if pulling to a branch besides master (useful for testing)\. If \fB\-\-no\-pbcopy\fR was passed, do not copy anything to the system If \fB\-\-no\-publish\fR was passed, do not publish bottles to Bintray\.
 .
 .TP
+\fBrelease\-notes\fR [\fIprevious_tag\fR] [\fIend_ref\fR]
+Output the merged pull requests on Homebrew/brew between two Git refs\. If no \fBprevious_tag\fR is provided it defaults to the newest tag\. If no \fBend_ref\fR is provided it defaults to \fBorigin/master\fR\.
+.
+.IP
+If \fB\-\-markdown\fR is passed, output as a Markdown list\.
+.
+.TP
 \fBtap\-new\fR \fIuser\fR\fB/\fR\fIrepo\fR
 Generate the template files for a new tap\.
 .