userdiff: add tests for Fortran xfuncname regex

The Fortran userdiff patterns, introduced in 909a5494f8 (userdiff.c: add
builtin fortran regex patterns, 2010-09-10), predate the test
infrastructure for xfuncname patterns, introduced in bfa7d01413 (t4018:
an infrastructure to test hunk headers, 2014-03-21).

Add tests for the Fortran xfuncname patterns. The test
't/t4018/fortran-comment-keyword' documents a shortcoming of the regex
that is fixed in a subsequent commit.

While at it, add descriptive comments for the different parts of the
regex.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/t/t4018/fortran-comment b/t/t4018/fortran-comment
new file mode 100644
index 0000000000..7b10d17658
--- /dev/null
+++ b/t/t4018/fortran-comment
@@ -0,0 +1,13 @@
+      module a
+
+      contains
+
+      ! subroutine wrong
+      subroutine RIGHT
+      ! subroutine wrong
+
+      real ChangeMe
+
+      end subroutine RIGHT
+
+      end module a