update: always report changes to branch 'master'

If the user's working copy is *not* on the 'master' branch, the revision
recorded after the update to the 'master' branch is not the one of the
updated 'master' branch but that of whatever the user's current branch
is. This tends to be not very helpful.

This change records the revision *after* the update to the 'master'
branch, but *before* switching back to the user's current branch prior
to the update, effectively causing the report to show changes to the
'master' branch.

Closes Homebrew/homebrew#42074.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

2 files changed, 10 insertions, 3 deletions

diff --git a/Library/Homebrew/cmd/update.rb b/Library/Homebrew/cmd/update.rb
index 200f03979..83350988b 100644
--- a/Library/Homebrew/cmd/update.rb
+++ b/Library/Homebrew/cmd/update.rb
@@ -194,6 +194,8 @@ class Updater
 
     reset_on_interrupt { safe_system "git", *args }
 
+    @current_revision = read_current_revision
+
     if @initial_branch != "master" && !@initial_branch.empty?
       safe_system "git", "checkout", @initial_branch, *quiet
     end
@@ -206,8 +208,6 @@ class Updater
       end
       @stashed = false
     end
-
-    @current_revision = read_current_revision
   end
 
   def reset_on_interrupt
@@ -224,6 +224,8 @@ class Updater
     map = Hash.new { |h, k| h[k] = [] }
 
     if initial_revision && initial_revision != current_revision
+      wc_revision = read_current_revision
+
       diff.each_line do |line|
         status, *paths = line.split
         src = paths.first
@@ -239,7 +241,11 @@ class Updater
           file = repository.join(src)
           begin
             formula = Formulary.factory(file)
-            new_version = formula.pkg_version
+            new_version = if wc_revision == current_revision
+              formula.pkg_version
+            else
+              FormulaVersions.new(formula).formula_at_revision(@current_revision, &:pkg_version)
+            end
             old_version = FormulaVersions.new(formula).formula_at_revision(@initial_revision, &:pkg_version)
             next if new_version == old_version
           rescue FormulaUnavailableError, *FormulaVersions::IGNORED_EXCEPTIONS => e
diff --git a/Library/Homebrew/test/test_updater.rb b/Library/Homebrew/test/test_updater.rb
index 9c3c02979..87e175ea3 100644
--- a/Library/Homebrew/test/test_updater.rb
+++ b/Library/Homebrew/test/test_updater.rb
@@ -64,6 +64,7 @@ class UpdaterTests < Homebrew::TestCase
     @updater.in_repo_expect("git pull --quiet origin refs/heads/master:refs/remotes/origin/master")
     @updater.in_repo_expect("git rev-parse -q --verify HEAD", "3456cdef")
     @updater.pull!(:silent => true)
+    @updater.in_repo_expect("git rev-parse -q --verify HEAD", "3456cdef")
     @report.update(@updater.report)
     assert_equal @updater.expected, @updater.called
   end