reverse sense of diffs (with `--show-diff` and `--verbose`)

[SethTisue]

the + vs - direction is the reverse of what you would expect

[som-snytt]

#81

Was git vs difflib:

# starting 1 test in neg
!! 1 - neg/t8300-overloading.scala               [output differs]
% diff /home/apm/projects/scala/test/files/neg/t8300-overloading-neg.log /home/apm/projects/scala/test/files/neg/t8300-overloading.check
@@ -1,5 +1,5 @@
 t8300-overloading.scala:15: error: double definition:
-def foo(name: Test.u.Name): Nothing at line 14 and
+def goo(name: Test.u.Name): Nothing at line 14 and
 def foo(name: Test.u.TermName): Nothing at line 15
 have same type after erasure: (name: Universe#NameApi)Nothing
   def foo(name: TermName) = ???

# 0/1 passed, 1 failed in neg

# Failed test paths (this command will update checkfiles)
partest --update-check \
  /home/apm/projects/scala/test/files/neg/t8300-overloading.scala


# starting 1 test in neg
!! 1 - neg/t8300-overloading.scala               [output differs]
% diff /home/apm/projects/scala/test/files/neg/t8300-overloading-neg.log /home/apm/projects/scala/test/files/neg/t8300-overloading.checkdiff /home/apm/projects/scala/test/files/neg/t8300-overloading-neg.log /home/apm/projects/scala/test/files/neg/t8300-overloading.check
--- t8300-overloading.check
+++ t8300-overloading-neg.log
@@ -1,3 +1,3 @@
 t8300-overloading.scala:15: error: double definition:
-def goo(name: Test.u.Name): Nothing at line 14 and
+def foo(name: Test.u.Name): Nothing at line 14 and
 def foo(name: Test.u.TermName): Nothing at line 15
# 0/1 passed, 1 failed in neg

# Failed test paths (this command will update checkfiles)
partest --update-check \
  /home/apm/projects/scala/test/files/neg/t8300-overloading.scala

Now:

# starting 1 test in neg
!! 1 - neg/t8300-overloading.scala               [output differs]
% diff /home/apm/projects/scala/test/files/neg/t8300-overloading-neg.log /home/apm/projects/scala/test/files/neg/t8300-overloading.check--- t8300-overloading-neg.log
+++ t8300-overloading.check
@@ -1,3 +1,3 @@
 t8300-overloading.scala:15: error: double definition:
-def foo(name: Test.u.Name): Nothing at line 14 and
+def goo(name: Test.u.Name): Nothing at line 14 and
 def foo(name: Test.u.TermName): Nothing at line 15
# 0/1 passed, 1 failed in neg

# Failed test paths (this command will update checkfiles)
partest --update-check \
  /home/apm/projects/scala/test/files/neg/t8300-overloading.scala