Merge branch 'jc/not-mingw-cygwin'

We have been using NOT_{MINGW,CYGWIN} test prerequisites long
before Peff invented support for negated prerequisites e.g. !MINGW
and we still add more uses of the former.  Convert them to the
latter to avoid confusion.

* jc/not-mingw-cygwin:
  test prerequisites: enumerate with commas
  test prerequisites: eradicate NOT_FOO

diff --cc t/t1402-check-ref-format.sh
index 4bc7141,28e9318..e5dc62e
--- 1/t/t1402-check-ref-format.sh
--- 2/t/t1402-check-ref-format.sh
+++ b/t/t1402-check-ref-format.sh
@@@ -120,15 -120,29 +120,15 @@@ invalid_ref "$ref" --refspec-patter
  invalid_ref "$ref" '--refspec-pattern --allow-onelevel'
  
  ref='/foo'
- invalid_ref NOT_MINGW "$ref"
- invalid_ref NOT_MINGW "$ref" --allow-onelevel
- invalid_ref NOT_MINGW "$ref" --refspec-pattern
- invalid_ref NOT_MINGW "$ref" '--refspec-pattern --allow-onelevel'
- invalid_ref NOT_MINGW "$ref" --normalize
- valid_ref NOT_MINGW "$ref" '--allow-onelevel --normalize'
- invalid_ref NOT_MINGW "$ref" '--refspec-pattern --normalize'
- valid_ref NOT_MINGW "$ref" '--refspec-pattern --allow-onelevel --normalize'
+ invalid_ref !MINGW "$ref"
+ invalid_ref !MINGW "$ref" --allow-onelevel
+ invalid_ref !MINGW "$ref" --refspec-pattern
+ invalid_ref !MINGW "$ref" '--refspec-pattern --allow-onelevel'
+ invalid_ref !MINGW "$ref" --normalize
+ valid_ref !MINGW "$ref" '--allow-onelevel --normalize'
+ invalid_ref !MINGW "$ref" '--refspec-pattern --normalize'
+ valid_ref !MINGW "$ref" '--refspec-pattern --allow-onelevel --normalize'
  
 -
 -valid_ref 'refs/heads/a-very-long-refname'
 -invalid_ref 'refs/heads/.a-very-long-refname'
 -invalid_ref 'refs/heads/abcdefgh0123..'
 -invalid_ref 'refs/heads/abcdefgh01234..'
 -invalid_ref 'refs/heads/abcdefgh012345..'
 -invalid_ref 'refs/heads/abcdefgh0123456..'
 -invalid_ref 'refs/heads/abcdefgh01234567..'
 -valid_ref 'refs/heads/abcdefgh0123.a'
 -valid_ref 'refs/heads/abcdefgh01234.a'
 -valid_ref 'refs/heads/abcdefgh012345.a'
 -valid_ref 'refs/heads/abcdefgh0123456.a'
 -valid_ref 'refs/heads/abcdefgh01234567.a'
 -
  test_expect_success "check-ref-format --branch @{-1}" '
        T=$(git write-tree) &&
        sha1=$(echo A | git commit-tree $T) &&

diff --cc t/test-lib.sh
Simple merge