patch 8.1.1740: exepath() doesn't work for "bin/cat"

Problem:    Exepath() doesn't work for "bin/cat".
Solution:   Check for any path separator. (Daniel Hahler, closes #4724,
            closes #4710)

src/evalfunc.c

@@ -3058,8 +3058,7 @@ f_executable(typval_T *argvars, typval_T *rettv)
     char_u *name = tv_get_string(&argvars[0]);
 
     /* Check in $PATH and also check directly if there is a directory name. */
-    rettv->vval.v_number = mch_can_exe(name, NULL, TRUE)
-		 || (gettail(name) != name && mch_can_exe(name, NULL, FALSE));
+    rettv->vval.v_number = mch_can_exe(name, NULL, TRUE);
 }
 
 static garray_T	redir_execute_ga;

src/os_unix.c

@@ -3103,12 +3103,11 @@ mch_can_exe(char_u *name, char_u **path, int use_path)
 
     /* When "use_path" is false and if it's an absolute or relative path don't
      * need to use $PATH. */
-    if (!use_path || mch_isFullName(name) || (name[0] == '.'
-		   && (name[1] == '/' || (name[1] == '.' && name[2] == '/'))))
+    if (!use_path || gettail(name) != name)
     {
 	/* There must be a path separator, files in the current directory
 	 * can't be executed. */
-	if (gettail(name) != name && executable_file(name))
+	if ((use_path || gettail(name) != name) && executable_file(name))
 	{
 	    if (path != NULL)
 	    {

src/testdir/test_functions.vim

@@ -990,6 +990,14 @@ func Test_Executable()
   elseif has('unix')
     call assert_equal(1, executable('cat'))
     call assert_equal(0, executable('nodogshere'))
+
+    " get "cat" path and remove the leading /
+    let catcmd = exepath('cat')[1:]
+    new
+    lcd /
+    call assert_equal(1, executable(catcmd))
+    call assert_equal('/' .. catcmd, exepath(catcmd))
+    bwipe
   endif
 endfunc
 

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1740,
 /**/
     1739,
 /**/