brew-deps: improved --tree formatting

Closes Homebrew/homebrew#40018.

Signed-off-by: Baptiste Fontaine <batifon@yahoo.fr>

Library/Homebrew/cmd/deps.rb

+# encoding: UTF-8
 require 'formula'
 require 'ostruct'
 
@@ -63,18 +64,25 @@ module Homebrew
   def puts_deps_tree(formulae)
     formulae.each do |f|
       puts f.full_name
-      recursive_deps_tree(f, 1)
+      recursive_deps_tree(f, "")
       puts
     end
   end
 
-  def recursive_deps_tree f, level
-    f.requirements.select(&:default_formula?).each do |req|
-      puts "|  "*(level-1) + "|- :#{req.to_dependency.name}"
+  def recursive_deps_tree f, prefix
+    reqs = f.requirements.select(&:default_formula?)
+    max = reqs.length - 1
+    reqs.each_with_index do |req, i|
+      chr = i == max ? "└──" : "├──"
+      puts prefix + "#{chr} :#{req.to_dependency.name}"
     end
-    f.deps.default.each do |dep|
-      puts "|  "*(level-1) + "|- #{dep.name}"
-      recursive_deps_tree(Formulary.factory(dep.name), level+1)
+    deps = f.deps.default
+    max = deps.length - 1
+    deps.each_with_index do |dep, i|
+      chr = i == max ? "└──" : "├──"
+      prefix_ext = i == max ? "    " : "|   "
+      puts prefix + "#{chr} #{dep.name}"
+      recursive_deps_tree(Formulary.factory(dep.name), prefix + prefix_ext)
     end
   end
 end