install: warn when passed no files

Rationale: we warn when inreplace makes no changes; this is a similar
sort of warning. We expected some list (probably via Dir) to include
some files, but none were found.

Either the list was wrong, or the install can now be omitted.

1 files changed, 8 insertions, 0 deletions

diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index 5ea924c9c..3adf6dfc2 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -8,8 +8,16 @@ class Pathname
     sources.each do |src|
       case src
       when Array
+        if src.empty?
+          opoo "install was passed an empty array"
+          return []
+        end
         src.each {|s| results << install_p(s) }
       when Hash
+        if src.empty?
+          opoo "install was passed an empty hash"
+          return []
+        end
         src.each {|s, new_basename| results << install_p(s, new_basename) }
       else
         results << install_p(src)