patch 8.2.0893: assert_equalfile() does not take a third argument

Problem:    Assert_equalfile() does not take a third argument.
Solution:   Implement the third argument. (Gary Johnson)

runtime/doc/eval.txt

@@ -2324,11 +2324,12 @@ argidx()			Number	current index in the argument list
 arglistid([{winnr} [, {tabnr}]]) Number	argument list id
 argv({nr} [, {winid}])		String	{nr} entry of the argument list
 argv([-1, {winid}])		List	the argument list
+asin({expr})			Float	arc sine of {expr}
 assert_beeps({cmd})		Number	assert {cmd} causes a beep
 assert_equal({exp}, {act} [, {msg}])
 				Number	assert {exp} is equal to {act}
-assert_equalfile({fname-one}, {fname-two})
+assert_equalfile({fname-one}, {fname-two} [, {msg}])
-				Number	assert file contents is equal
+				Number	assert file contents are equal
 assert_exception({error} [, {msg}])
 				Number	assert {error} is in v:exception
 assert_fails({cmd} [, {error} [, {msg}]])

runtime/doc/testing.txt

@@ -263,9 +263,8 @@ assert_equal({expected}, {actual} [, {msg}])
 		Can also be used as a |method|: >
 			mylist->assert_equal([1, 2, 3])
 
-
 <							*assert_equalfile()*
-assert_equalfile({fname-one}, {fname-two})
+assert_equalfile({fname-one}, {fname-two} [, {msg}])
 		When the files {fname-one} and {fname-two} do not contain
 		exactly the same text an error message is added to |v:errors|.
 		Also see |assert-return|.
@@ -276,7 +275,6 @@ assert_equalfile({fname-one}, {fname-two})
 		Can also be used as a |method|: >
 			GetLog()->assert_equalfile('expected.log')
 
-
 assert_exception({error} [, {msg}])			*assert_exception()*
 		When v:exception does not contain the string {error} an error
 		message is added to |v:errors|.  Also see |assert-return|.

src/evalfunc.c

@@ -419,7 +419,7 @@ static funcentry_T global_functions[] =
     {"asin",		1, 1, FEARG_1,	  ret_float,	FLOAT_FUNC(f_asin)},
     {"assert_beeps",	1, 2, FEARG_1,	  ret_number,	f_assert_beeps},
     {"assert_equal",	2, 3, FEARG_2,	  ret_number,	f_assert_equal},
-    {"assert_equalfile", 2, 2, FEARG_1,	  ret_number,	f_assert_equalfile},
+    {"assert_equalfile", 2, 3, FEARG_1,	  ret_number,	f_assert_equalfile},
     {"assert_exception", 1, 2, 0,	  ret_number,	f_assert_exception},
     {"assert_fails",	1, 3, FEARG_1,	  ret_number,	f_assert_fails},
     {"assert_false",	1, 2, FEARG_1,	  ret_number,	f_assert_false},

src/testdir/test_assert.vim

@@ -81,6 +81,10 @@ func Test_assert_equalfile()
   call assert_match("difference at byte 4", v:errors[0])
   call remove(v:errors, 0)
 
+  call assert_equal(1, assert_equalfile('Xone', 'Xtwo', 'a message'))
+  call assert_match("a message: difference at byte 4", v:errors[0])
+  call remove(v:errors, 0)
+
   call delete('Xone')
   call delete('Xtwo')
 endfunc

src/testing.c

@@ -362,6 +362,15 @@ assert_equalfile(typval_T *argvars)
     if (IObuff[0] != NUL)
     {
 	prepare_assert_error(&ga);
+	if (argvars[2].v_type != VAR_UNKNOWN)
+	{
+	    char_u	numbuf[NUMBUFLEN];
+	    char_u	*tofree;
+
+	    ga_concat(&ga, echo_string(&argvars[2], &tofree, numbuf, 0));
+	    vim_free(tofree);
+	    ga_concat(&ga, (char_u *)": ");
+	}
 	ga_concat(&ga, IObuff);
 	assert_error(&ga);
 	ga_clear(&ga);
@@ -371,7 +380,7 @@ assert_equalfile(typval_T *argvars)
 }
 
 /*
- * "assert_equalfile(fname-one, fname-two)" function
+ * "assert_equalfile(fname-one, fname-two[, msg])" function
  */
     void
 f_assert_equalfile(typval_T *argvars, typval_T *rettv)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    893,
 /**/
     892,
 /**/