Remove open_file_unit and associated interface

No longer need this function, since the other one uses the internal unit
of file_type.

Also, might as well switch the .testing Makefile to check the FMS2
infra (although this really ought to be configurable, if not active over
all infra).

.testing/Makefile

@@ -173,11 +173,11 @@ SOURCE = \
   $(foreach ext,F90 inc c h,$(wildcard $(1)/*/*.$(ext) $(1)/*/*/*.$(ext)))
 
 MOM_SOURCE = $(call SOURCE,../src) \
-  $(wildcard ../config_src/infra/FMS1/*.F90) \
+  $(wildcard ../config_src/infra/FMS2/*.F90) \
   $(wildcard ../config_src/drivers/solo_driver/*.F90) \
   $(wildcard ../config_src/ext*/*/*.F90)
 TARGET_SOURCE = $(call SOURCE,build/target_codebase/src) \
-  $(wildcard build/target_codebase/config_src/infra/FMS1/*.F90) \
+  $(wildcard build/target_codebase/config_src/infra/FMS2/*.F90) \
   $(wildcard build/target_codebase/config_src/drivers/solo_driver/*.F90) \
   $(wildcard build/target_codebase/config_src/ext*/*.F90)
 FMS_SOURCE = $(call SOURCE,$(DEPS)/fms/src)

config_src/infra/FMS2/MOM_io_infra.F90

@@ -61,11 +61,6 @@ module MOM_io_infra
   module procedure MOM_file_exists
 end interface
 
-!> Open a file (or fileset) for parallel or single-file I/O.
-interface open_file
-  module procedure open_file_type, open_file_unit
-end interface open_file
-
 !> Read a data field from a file
 interface read_field
   module procedure read_field_4d
@@ -260,35 +255,7 @@ subroutine write_version(version, tag, unit)
 end subroutine write_version
 
 !> open_file opens a file for parallel or single-file I/O.
-subroutine open_file_unit(unit, filename, action, form, threading, fileset, nohdrs, domain, MOM_domain)
-  integer,                  intent(out) :: unit   !< The I/O unit for the opened file
-  character(len=*),         intent(in)  :: filename !< The name of the file being opened
-  integer,        optional, intent(in)  :: action !< A flag indicating whether the file can be read
-                                                  !! or written to and how to handle existing files.
-  integer,        optional, intent(in)  :: form   !< A flag indicating the format of a new file.  The
-                                                  !! default is ASCII_FILE, but NETCDF_FILE is also common.
-  integer,        optional, intent(in)  :: threading !< A flag indicating whether one (SINGLE_FILE)
-                                                  !! or multiple PEs (MULTIPLE) participate in I/O.
-                                                  !! With the default, the root PE does I/O.
-  integer,        optional, intent(in)  :: fileset !< A flag indicating whether multiple PEs doing I/O due
-                                                  !! to threading=MULTIPLE write to the same file (SINGLE_FILE)
-                                                  !! or to one file per PE (MULTIPLE, the default).
-  logical,        optional, intent(in)  :: nohdrs !< If nohdrs is .TRUE., headers are not written to
-                                                  !! ASCII files.  The default is .false.
-  type(domain2d), optional, intent(in)  :: domain !< A domain2d type that describes the decomposition
-  type(MOM_domain_type), optional, intent(in) :: MOM_Domain !< A MOM_Domain that describes the decomposition
-
-  if (present(MOM_Domain)) then
-    call mpp_open(unit, filename, action=action, form=form, threading=threading, fileset=fileset, &
-                  nohdrs=nohdrs, domain=MOM_Domain%mpp_domain)
-  else
-    call mpp_open(unit, filename, action=action, form=form, threading=threading, fileset=fileset, &
-                  nohdrs=nohdrs, domain=domain)
-  endif
-end subroutine open_file_unit
-
-!> open_file opens a file for parallel or single-file I/O.
-subroutine open_file_type(IO_handle, filename, action, MOM_domain, threading, fileset)
+subroutine open_file(IO_handle, filename, action, MOM_domain, threading, fileset)
   type(file_type),          intent(inout) :: IO_handle !< The handle for the opened file
   character(len=*),         intent(in)    :: filename !< The path name of the file being opened
   integer,        optional, intent(in)    :: action !< A flag indicating whether the file can be read
@@ -316,12 +283,12 @@ subroutine open_file_type(IO_handle, filename, action, MOM_domain, threading, fi
   integer :: index_nc
 
   if (IO_handle%open_to_write) then
-    call MOM_error(WARNING, "open_file_type called for file "//trim(filename)//&
+    call MOM_error(WARNING, "open_file called for file "//trim(filename)//&
         " with an IO_handle that is already open to to write.")
     return
   endif
   if (IO_handle%open_to_read) then
-    call MOM_error(FATAL, "open_file_type called for file "//trim(filename)//&
+    call MOM_error(FATAL, "open_file called for file "//trim(filename)//&
         " with an IO_handle that is already open to to read.")
   endif
 
@@ -344,7 +311,7 @@ subroutine open_file_type(IO_handle, filename, action, MOM_domain, threading, fi
     elseif (file_mode == OVERWRITE_FILE) then ; mode = "overwrite"
     elseif (file_mode == READONLY_FILE) then ; mode = "read"
     else
-      call MOM_error(FATAL, "open_file_type called with unrecognized action.")
+      call MOM_error(FATAL, "open_file called with unrecognized action.")
     endif
 
     IO_handle%num_times = 0
@@ -381,7 +348,7 @@ subroutine open_file_type(IO_handle, filename, action, MOM_domain, threading, fi
     IO_handle%open_to_read = .false. ; IO_handle%open_to_write = .true.
   endif
 
-end subroutine open_file_type
+end subroutine open_file
 
 !> open_file opens an ascii file for parallel or single-file I/O using Fortran read and write calls.
 subroutine open_ASCII_file(unit, file, action, threading, fileset)