create: use GitHub metadata where available.

GitHub provides a description and homepage field so let `brew create`
use them where possible. Also, detect GitHub repositories based on
`releases` as well as `archive`s.

Library/Homebrew/dev-cmd/create.rb

@@ -10,7 +10,8 @@
 #:    If `--meson` is passed, create a basic template for a Meson-style build.
 #:
 #:    If `--no-fetch` is passed, Homebrew will not download <URL> to the cache and
-#:    will thus not add the SHA256 to the formula for you.
+#:    will thus not add the SHA256 to the formula for you. It will also not check
+#:    the GitHub API for GitHub projects (to fill out the description and homepage).
 #:
 #:    The options `--set-name` and `--set-version` each take an argument and allow
 #:    you to explicitly set the name and version of the package you are creating.
@@ -100,7 +101,7 @@ module Homebrew
 end
 
 class FormulaCreator
-  attr_reader :url, :sha256
+  attr_reader :url, :sha256, :desc, :homepage
   attr_accessor :name, :version, :tap, :path, :mode
 
   def url=(url)
@@ -108,11 +109,15 @@ class FormulaCreator
     path = Pathname.new(url)
     if @name.nil?
       case url
-      when %r{github\.com/\S+/(\S+)\.git}
-        @name = $1
+      when %r{github\.com/(\S+)/(\S+)\.git}
+        @user = $1
+        @name = $2
         @head = true
-      when %r{github\.com/\S+/(\S+)/archive/}
-        @name = $1
+        @github = true
+      when %r{github\.com/(\S+)/(\S+)/(archive|releases)/}
+        @user = $1
+        @name = $2
+        @github = true
       else
         @name = path.basename.to_s[/(.*?)[-_.]?#{Regexp.escape(path.version.to_s)}/, 1]
       end
@@ -131,7 +136,7 @@ class FormulaCreator
   end
 
   def fetch?
-    !head? && !ARGV.include?("--no-fetch")
+    !ARGV.include?("--no-fetch")
   end
 
   def head?
@@ -145,11 +150,25 @@ class FormulaCreator
       opoo "Version cannot be determined from URL."
       puts "You'll need to add an explicit 'version' to the formula."
     elsif fetch?
-      r = Resource.new
-      r.url(url)
-      r.version(version)
-      r.owner = self
-      @sha256 = r.fetch.sha256 if r.download_strategy == CurlDownloadStrategy
+      unless head?
+        r = Resource.new
+        r.url(url)
+        r.version(version)
+        r.owner = self
+        @sha256 = r.fetch.sha256 if r.download_strategy == CurlDownloadStrategy
+      end
+
+      if @user && @name
+        begin
+          metadata = GitHub.repository(@user, @name)
+          @desc = metadata["description"]
+          @homepage = metadata["homepage"]
+        rescue GitHub::HTTPNotFoundError
+          # If there was no repository found assume the network connection is at
+          # fault rather than the input URL.
+          nil
+        end
+      end
     end
 
     path.write ERB.new(template, nil, ">").result(binding)
@@ -161,8 +180,8 @@ class FormulaCreator
     # PLEASE REMOVE ALL GENERATED COMMENTS BEFORE SUBMITTING YOUR PULL REQUEST!
 
     class #{Formulary.class_s(name)} < Formula
-      desc ""
-      homepage ""
+      desc "#{desc}"
+      homepage "#{homepage}"
     <% if head? %>
       head "#{url}"
     <% else %>

docs/Manpage.md

@@ -709,7 +709,8 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     If `--meson` is passed, create a basic template for a Meson-style build.
 
     If `--no-fetch` is passed, Homebrew will not download `URL` to the cache and
-    will thus not add the SHA256 to the formula for you.
+    will thus not add the SHA256 to the formula for you. It will also not check
+    the GitHub API for GitHub projects (to fill out the description and homepage).
 
     The options `--set-name` and `--set-version` each take an argument and allow
     you to explicitly set the name and version of the package you are creating.

manpages/brew.1

@@ -729,7 +729,7 @@ Generate a formula for the downloadable file at \fIURL\fR and open it in the edi
 If \fB\-\-autotools\fR is passed, create a basic template for an Autotools\-style build\. If \fB\-\-cmake\fR is passed, create a basic template for a CMake\-style build\. If \fB\-\-meson\fR is passed, create a basic template for a Meson\-style build\.
 .
 .IP
-If \fB\-\-no\-fetch\fR is passed, Homebrew will not download \fIURL\fR to the cache and will thus not add the SHA256 to the formula for you\.
+If \fB\-\-no\-fetch\fR is passed, Homebrew will not download \fIURL\fR to the cache and will thus not add the SHA256 to the formula for you\. It will also not check the GitHub API for GitHub projects (to fill out the description and homepage)\.
 .
 .IP
 The options \fB\-\-set\-name\fR and \fB\-\-set\-version\fR each take an argument and allow you to explicitly set the name and version of the package you are creating\.