getdigits: introduce strict, def parameters

Problem:
During a refactor long ago, we changed the `getdigits_*` familiy of
functions to abort on overflow.  But this is often wrong, because many
of these codepaths are handling user input.

Solution:
Decide at each call-site whether to use "strict" mode.

fix #5555

src/nvim/ex_docmd.c

@@ -2071,7 +2071,7 @@ static char_u * do_one_cmd(char_u **cmdlinep,
   if ((ea.argt & COUNT) && ascii_isdigit(*ea.arg)
       && (!(ea.argt & BUFNAME) || *(p = skipdigits(ea.arg)) == NUL
           || ascii_iswhite(*p))) {
-    n = getdigits_long(&ea.arg);
+    n = getdigits_long(&ea.arg, false, -1);
     ea.arg = skipwhite(ea.arg);
     if (n <= 0 && !ni && (ea.argt & ZEROR) == 0) {
       errormsg = (char_u *)_(e_zerocount);
@@ -3797,7 +3797,7 @@ static linenr_T get_address(exarg_T *eap,
 
     default:
       if (ascii_isdigit(*cmd))                    /* absolute line number */
-        lnum = getdigits_long(&cmd);
+        lnum = getdigits_long(&cmd, false, 0);
     }
 
     for (;; ) {
@@ -3832,14 +3832,16 @@ static linenr_T get_address(exarg_T *eap,
         }
       }
 
-      if (ascii_isdigit(*cmd))
-        i = '+';                        /* "number" is same as "+number" */
-      else
+      if (ascii_isdigit(*cmd)) {
+        i = '+';                        // "number" is same as "+number"
+      } else {
         i = *cmd++;
-      if (!ascii_isdigit(*cmd))           /* '+' is '+1', but '+0' is not '+1' */
+      }
+      if (!ascii_isdigit(*cmd)) {       // '+' is '+1', but '+0' is not '+1'
         n = 1;
-      else
-        n = getdigits(&cmd);
+      } else {
+        n = getdigits(&cmd, true, 0);
+      }
 
       if (addr_type == ADDR_TABS_RELATIVE) {
         EMSG(_(e_invrange));
@@ -4504,7 +4506,7 @@ static int get_tabpage_arg(exarg_T *eap)
     }
 
     p_save = p;
-    tab_number = getdigits(&p);
+    tab_number = getdigits(&p, false, tab_number);
 
     if (relative == 0) {
       if (STRCMP(p, "$") == 0) {
@@ -5179,7 +5181,7 @@ two_count:
           return FAIL;
         }
 
-        *def = getdigits_long(&p);
+        *def = getdigits_long(&p, true, 0);
         *argt |= (ZEROR | NOTADR);
 
         if (p != val + vallen || vallen == 0) {
@@ -5196,7 +5198,7 @@ invalid_count:
         if (*def >= 0)
           goto two_count;
 
-        *def = getdigits_long(&p);
+        *def = getdigits_long(&p, true, 0);
 
         if (p != val + vallen)
           goto invalid_count;
@@ -6832,8 +6834,7 @@ static void ex_tabnext(exarg_T *eap)
     if (eap->arg && *eap->arg != NUL) {
       char_u *p = eap->arg;
       char_u *p_save = p;
-
-      tab_number = getdigits(&p);
+      tab_number = getdigits(&p, false, 0);
       if (p == p_save || *p_save == '-' || *p_save == '+' || *p != NUL
           || tab_number == 0) {
         // No numbers as argument.
@@ -7472,18 +7473,16 @@ static void do_exmap(exarg_T *eap, int isabbrev)
  */
 static void ex_winsize(exarg_T *eap)
 {
-  int w, h;
-  char_u      *arg = eap->arg;
-  char_u      *p;
-
-  w = getdigits_int(&arg);
+  char_u *arg = eap->arg;
+  int w = getdigits_int(&arg, false, 10);
   arg = skipwhite(arg);
-  p = arg;
-  h = getdigits_int(&arg);
-  if (*p != NUL && *arg == NUL)
+  char_u *p = arg;
+  int h = getdigits_int(&arg, false, 10);
+  if (*p != NUL && *arg == NUL) {
     screen_resize(w, h);
-  else
+  } else {
     EMSG(_("E465: :winsize requires two number arguments"));
+  }
 }
 
 static void ex_wincmd(exarg_T *eap)
@@ -7745,7 +7744,7 @@ static void ex_later(exarg_T *eap)
   if (*p == NUL)
     count = 1;
   else if (isdigit(*p)) {
-    count = getdigits_long(&p);
+    count = getdigits_long(&p, false, 0);
     switch (*p) {
     case 's': ++p; sec = true; break;
     case 'm': ++p; sec = true; count *= 60; break;
@@ -8414,7 +8413,7 @@ static void ex_findpat(exarg_T *eap)
 
   n = 1;
   if (ascii_isdigit(*eap->arg)) { /* get count */
-    n = getdigits_long(&eap->arg);
+    n = getdigits_long(&eap->arg, false, 0);
     eap->arg = skipwhite(eap->arg);
   }
   if (*eap->arg == '/') {   /* Match regexp, not just whole words */
@@ -8660,13 +8659,13 @@ eval_vars (
       return NULL;
     }
   }
-  /*
-   * '#': Alternate file name
-   * '%': Current file name
-   *	    File name under the cursor
-   *	    File name for autocommand
-   *	and following modifiers
-   */
+  //
+  // '#': Alternate file name
+  // '%': Current file name
+  //        File name under the cursor
+  //        File name for autocommand
+  //    and following modifiers
+  //
   else {
     switch (spec_idx) {
     case SPEC_PERC:             /* '%': current file */
@@ -8692,7 +8691,7 @@ eval_vars (
       s = src + 1;
       if (*s == '<')                    /* "#<99" uses v:oldfiles */
         ++s;
-      i = getdigits_int(&s);
+      i = getdigits_int(&s, false, 0);
       if (s == src + 2 && src[1] == '-') {
         // just a minus sign, don't skip over it
         s--;