update-test: allow setting start commit

To use origin/master as start commit
  brew update-test

To use <sha1> as start commit
  brew update-test --commit=<sha1>

To use commit at <date> as start commit
  brew update-test --before=<date>

Also print start/end commit for debug purpose

1 files changed, 16 insertions, 1 deletions

diff --git a/Library/Homebrew/dev-cmd/update-test.rb b/Library/Homebrew/dev-cmd/update-test.rb
index 38220da26..b32dcf45a 100644
--- a/Library/Homebrew/dev-cmd/update-test.rb
+++ b/Library/Homebrew/dev-cmd/update-test.rb
@@ -1,11 +1,26 @@
 require "extend/ENV"
 
 module Homebrew
+  #
+  # Usage:
+  #    brew update-test                 # using origin/master as start commit
+  #    brew update-test --commit=<sha1> # using <sha1> as start commit
+  #    brew update-test --before=<date> # using commit at <date> as start commit
+  #
   def update_test
     cd HOMEBREW_REPOSITORY
-    start_sha1 = Utils.popen_read("git", "rev-parse", "origin/master").chomp
+    start_sha1 = if commit = ARGV.value("commit")
+      commit
+    elsif date = ARGV.value("before")
+      Utils.popen_read("git", "rev-list", "-n1", "--before=#{date}", "origin/master").chomp
+    else
+      Utils.popen_read("git", "rev-parse", "origin/master").chomp
+     end
     end_sha1 = Utils.popen_read("git", "rev-parse", "HEAD").chomp
 
+    puts "Start commit: #{start_sha1}"
+    puts "End   commit: #{end_sha1}"
+
     mktemp do
       curdir = Pathname.new(Dir.pwd)