update-test: improve error handling.

Fail if the start or end commit are missing and retry finding the
previous tag by fetching all tags if they are missing.

This should fix CI on the current Homebrew/brew `master` branch.

Closes #2404.

1 files changed, 13 insertions, 1 deletions

diff --git a/Library/Homebrew/dev-cmd/update-test.rb b/Library/Homebrew/dev-cmd/update-test.rb
index 2ff168669..3cf095f2b 100644
--- a/Library/Homebrew/dev-cmd/update-test.rb
+++ b/Library/Homebrew/dev-cmd/update-test.rb
@@ -33,12 +33,24 @@ module Homebrew
     elsif date = ARGV.value("before")
       Utils.popen_read("git", "rev-list", "-n1", "--before=#{date}", "origin/master").chomp
     elsif ARGV.include?("--to-tag")
-      Utils.popen_read("git", "tag", "--list", "--sort=-version:refname").lines[1].chomp
+      previous_tag =
+        Utils.popen_read("git", "tag", "--list", "--sort=-version:refname").lines[1]
+      unless previous_tag
+        safe_system "git", "fetch", "--tags"
+        previous_tag =
+          Utils.popen_read("git", "tag", "--list", "--sort=-version:refname").lines[1]
+      end
+      previous_tag.to_s.chomp
     else
       Utils.popen_read("git", "rev-parse", "origin/master").chomp
     end
+    odie "Could not find start commit!" if start_commit.empty?
+
     start_commit = Utils.popen_read("git", "rev-parse", start_commit).chomp
+    odie "Could not find start commit!" if start_commit.empty?
+
     end_commit = Utils.popen_read("git", "rev-parse", "HEAD").chomp
+    odie "Could not find end commit!" if end_commit.empty?
 
     puts "Start commit: #{start_commit}"
     puts "End   commit: #{end_commit}"