#474: Anchor Fbe.mask_to_regex regex to prevent prefix collisions (#495)

* fix: anchor Fbe.mask_to_regex regex to prevent prefix collisions

The regex built by Fbe.mask_to_regex was unanchored, so
re.match? would match substrings. For exclusion masks like
'-zerocracy/judges-action', this caused repositories with
prefix collisions (e.g. 'zerocracy/judges-actions' or
'zerocracy/judges-action-old') to be incorrectly excluded.

Added \A and \z anchors to ensure full-string matching.
Wildcard masks (zerocracy/*) are unaffected since .*
already absorbs the entire tail.

Added four direct unit tests for Fbe.mask_to_regex:
- test_mask_to_regex_exact_match
- test_mask_to_regex_prefix_collision
- test_mask_to_regex_wildcard
- test_mask_to_regex_case_insensitive

* fix: update off_quota assertion for search threshold

Author: VasilevNStas

lib/fbe/unmask_repos.rb

@@ -24,7 +24,7 @@
 def Fbe.mask_to_regex(mask)
   org, repo = mask.split('/')
   raise(Fbe::Error, "Org '#{org}' can't have an asterisk") if org.include?('*')
-  Regexp.compile("#{Regexp.escape(org)}/#{Regexp.escape(repo).gsub('\\*', '.*')}", Regexp::IGNORECASE)
+  Regexp.compile("\\A#{Regexp.escape(org)}/#{Regexp.escape(repo).gsub('\\*', '.*')}\\z", Regexp::IGNORECASE)
 end
 
 # Resolves repository masks to actual GitHub repository names.

test/fbe/test_unmask_repos.rb

@@ -70,6 +70,28 @@ def test_mask_to_regex_still_expands_wildcard
     refute_match(re, 'zold-io/blogXzoldYio')
   end
 
+  def test_mask_to_regex_exact_match
+    re = Fbe.mask_to_regex('zerocracy/judges-action')
+    assert_match(re, 'zerocracy/judges-action')
+  end
+
+  def test_mask_to_regex_prefix_collision
+    re = Fbe.mask_to_regex('zerocracy/judges-action')
+    refute_match(re, 'zerocracy/judges-actions')
+    refute_match(re, 'zerocracy/judges-action-old')
+  end
+
+  def test_mask_to_regex_wildcard
+    re = Fbe.mask_to_regex('zerocracy/*')
+    assert_match(re, 'zerocracy/fbe')
+    assert_match(re, 'zerocracy/judges-action')
+  end
+
+  def test_mask_to_regex_case_insensitive
+    re = Fbe.mask_to_regex('Zerocracy/Fbe')
+    assert_match(re, 'zerocracy/fbe')
+  end
+
   def test_live_usage
     skip('Run it only manually, since it touches GitHub API')
     opts = Judges::Options.new({ 'repositories' => 'zerocracy/*,-zerocracy/judges-action,zerocracy/datum' })