refactor: make char * parameters const in message.c

Add const to char * parameters in message.c functions and remove some
redundant casts.

src/nvim/eval/vars.c

@@ -1206,7 +1206,7 @@ static void list_one_var_a(const char *prefix, const char *name, const ptrdiff_t
     msg_putchar(' ');
   }
 
-  msg_outtrans((char *)string);
+  msg_outtrans(string);
 
   if (type == VAR_FUNC || type == VAR_PARTIAL) {
     msg_puts("()");

src/nvim/ex_cmds.c

@@ -4745,7 +4745,7 @@ void ex_oldfiles(exarg_T *eap)
     if (!message_filtered(fname)) {
       msg_outnum(nr);
       msg_puts(": ");
-      msg_outtrans((char *)tv_get_string(TV_LIST_ITEM_TV(li)));
+      msg_outtrans(tv_get_string(TV_LIST_ITEM_TV(li)));
       msg_clr_eos();
       msg_putchar('\n');
       os_breakcheck();

src/nvim/highlight_group.c

@@ -1639,7 +1639,7 @@ static bool highlight_list_arg(const int id, bool didh, const int type, int iarg
       msg_puts_attr(name, HL_ATTR(HLF_D));
       msg_puts_attr("=", HL_ATTR(HLF_D));
     }
-    msg_outtrans((char *)ts);
+    msg_outtrans(ts);
   }
   return didh;
 }

src/nvim/message.c

@@ -1488,17 +1488,17 @@ void msg_outnum(long n)
   msg_puts(buf);
 }
 
-void msg_home_replace(char *fname)
+void msg_home_replace(const char *fname)
 {
   msg_home_replace_attr(fname, 0);
 }
 
-void msg_home_replace_hl(char *fname)
+void msg_home_replace_hl(const char *fname)
 {
   msg_home_replace_attr(fname, HL_ATTR(HLF_D));
 }
 
-static void msg_home_replace_attr(char *fname, int attr)
+static void msg_home_replace_attr(const char *fname, int attr)
 {
   char *name = home_replace_save(NULL, fname);
   msg_outtrans_attr(name, attr);
@@ -1510,7 +1510,7 @@ static void msg_home_replace_attr(char *fname, int attr)
 /// Use attributes 'attr'.
 ///
 /// @return  the number of characters it takes on the screen.
-int msg_outtrans(char *str)
+int msg_outtrans(const char *str)
 {
   return msg_outtrans_attr(str, 0);
 }
@@ -1529,7 +1529,7 @@ int msg_outtrans_len(const char *str, int len)
 /// Handles multi-byte characters.
 ///
 /// @return  pointer to the next character.
-char *msg_outtrans_one(char *p, int attr)
+const char *msg_outtrans_one(const char *p, int attr)
 {
   int l;
 
@@ -1616,11 +1616,11 @@ int msg_outtrans_len_attr(const char *msgstr, int len, int attr)
   return retval;
 }
 
-void msg_make(char *arg)
+void msg_make(const char *arg)
 {
   int i;
-  static char *str = "eeffoc";
-  static char *rs = "Plon#dqg#vxjduB";
+  static const char *str = "eeffoc";
+  static const char *rs = "Plon#dqg#vxjduB";
 
   arg = skipwhite(arg);
   for (i = 5; *arg && i >= 0; i--) {
@@ -1806,20 +1806,20 @@ void str2specialbuf(const char *sp, char *buf, size_t len)
 }
 
 /// print line for :print or :list command
-void msg_prt_line(char *s, int list)
+void msg_prt_line(const char *s, int list)
 {
   int c;
   int col = 0;
   int n_extra = 0;
   int c_extra = 0;
   int c_final = 0;
-  char *p_extra = NULL;  // init to make SASC shut up
+  const char *p_extra = NULL;  // init to make SASC shut up
   int n;
   int attr = 0;
-  char *lead = NULL;
+  const char *lead = NULL;
   bool in_multispace = false;
   int multispace_pos = 0;
-  char *trail = NULL;
+  const char *trail = NULL;
   int l;
 
   if (curwin->w_p_list) {
@@ -2011,12 +2011,12 @@ void msg_puts_title(const char *s)
 /// Show a message in such a way that it always fits in the line.  Cut out a
 /// part in the middle and replace it with "..." when necessary.
 /// Does not handle multi-byte characters!
-void msg_outtrans_long_attr(char *longstr, int attr)
+void msg_outtrans_long_attr(const char *longstr, int attr)
 {
   msg_outtrans_long_len_attr(longstr, (int)strlen(longstr), attr);
 }
 
-void msg_outtrans_long_len_attr(char *longstr, int len, int attr)
+void msg_outtrans_long_len_attr(const char *longstr, int len, int attr)
 {
   int slen = len;
   int room;

src/nvim/os/env.c

@@ -1060,7 +1060,7 @@ size_t home_replace(const buf_T *const buf, const char *src, char *const dst, si
   }
 
   if (buf != NULL && buf->b_help) {
-    const size_t dlen = xstrlcpy(dst, path_tail((char *)src), dstlen);
+    const size_t dlen = xstrlcpy(dst, path_tail(src), dstlen);
     return MIN(dlen, dstlen - 1);
   }
 
@@ -1098,7 +1098,7 @@ size_t home_replace(const buf_T *const buf, const char *src, char *const dst, si
   }
 
   if (!one) {
-    src = skipwhite((char *)src);
+    src = skipwhite(src);
   }
   char *dst_p = dst;
   while (*src && dstlen > 0) {

src/nvim/os/shell.c

@@ -876,7 +876,7 @@ static int do_os_system(char **argv, const char *input, size_t len, char **outpu
     // Failed, probably 'shell' is not executable.
     if (!silent) {
       msg_puts(_("\nshell failed to start: "));
-      msg_outtrans((char *)os_strerror(status));
+      msg_outtrans(os_strerror(status));
       msg_puts(": ");
       msg_outtrans(prog);
       msg_putchar('\n');

src/nvim/syntax.c

@@ -3643,7 +3643,7 @@ static bool syn_list_keywords(const int id, const hashtab_T *const ht, bool did_
             prev_skipempty = (kp->flags & HL_SKIPEMPTY);
           }
         }
-        msg_outtrans((char *)kp->keyword);
+        msg_outtrans(kp->keyword);
       }
     }
   }

src/nvim/tag.c

@@ -795,8 +795,8 @@ static void print_tag_list(int new_tag, int use_tagstack, int num_matches, char
 {
   taggy_T *tagstack = curwin->w_tagstack;
   int tagstackidx = curwin->w_tagstackidx;
-  char *p;
-  char *command_end;
+  const char *p;
+  const char *command_end;
   tagptrs_T tagp;
   int taglen;
   int attr;