refactor: collapse statements in single assignments

Problem:

Variables are often assigned multiple places in common patterns.

Solution:

Replace these common patterns with different patterns that reduce the
number of assignments.

Use `MAX` and `MIN`:
```c
if (x < y) {
  x = y;
}

// -->

x = MAX(x, y);
```

```c
if (x > y) {
  x = y;
}

// -->

x = MIN(x, y);
```

Use ternary:
```c
int a;
if (cond) {
  a = b;
} els {
  a = c;
}

// -->

int a = cond ? b : c;

```

src/nvim/ex_getln.c

@@ -390,13 +390,8 @@ static bool do_incsearch_highlighting(int firstc, int *search_delim, incsearch_s
   parse_cmd_address(&ea, &dummy, true);
   if (ea.addr_count > 0) {
     // Allow for reverse match.
-    if (ea.line2 < ea.line1) {
-      search_first_line = ea.line2;
-      search_last_line = ea.line1;
-    } else {
-      search_first_line = ea.line1;
-      search_last_line = ea.line2;
-    }
+    search_first_line = MIN(ea.line1, ea.line1);
+    search_last_line = MAX(ea.line2, ea.line1);
   } else if (cmd[0] == 's' && cmd[1] != 'o') {
     // :s defaults to the current line
     search_first_line = curwin->w_cursor.lnum;
@@ -1034,11 +1029,7 @@ static int command_line_handle_ctrl_bsl(CommandLineState *s)
 
         // Restore the cursor or use the position set with
         // set_cmdline_pos().
-        if (new_cmdpos > ccline.cmdlen) {
-          ccline.cmdpos = ccline.cmdlen;
-        } else {
-          ccline.cmdpos = new_cmdpos;
-        }
+        ccline.cmdpos = MIN(ccline.cmdlen, new_cmdpos);
 
         KeyTyped = false;                 // Don't do p_wc completion.
         redrawcmd();
@@ -1658,11 +1649,7 @@ static int command_line_insert_reg(CommandLineState *s)
     KeyTyped = false;                // Don't do p_wc completion.
     if (new_cmdpos >= 0) {
       // set_cmdline_pos() was used
-      if (new_cmdpos > ccline.cmdlen) {
-        ccline.cmdpos = ccline.cmdlen;
-      } else {
-        ccline.cmdpos = new_cmdpos;
-      }
+      ccline.cmdpos = MIN(ccline.cmdlen, new_cmdpos);
     }
   }
   new_cmdpos = save_new_cmdpos;
@@ -3546,10 +3533,6 @@ void unputcmdline(void)
 // called afterwards.
 void put_on_cmdline(const char *str, int len, bool redraw)
 {
-  int i;
-  int m;
-  int c;
-
   if (len < 0) {
     len = (int)strlen(str);
   }
@@ -3563,7 +3546,8 @@ void put_on_cmdline(const char *str, int len, bool redraw)
     ccline.cmdlen += len;
   } else {
     // Count nr of characters in the new string.
-    m = 0;
+    int m = 0;
+    int i;
     for (i = 0; i < len; i += utfc_ptr2len(str + i)) {
       m++;
     }
@@ -3587,8 +3571,8 @@ void put_on_cmdline(const char *str, int len, bool redraw)
   {
     // When the inserted text starts with a composing character,
     // backup to the character before it.  There could be two of them.
-    i = 0;
-    c = utf_ptr2char(ccline.cmdbuff + ccline.cmdpos);
+    int i = 0;
+    int c = utf_ptr2char(ccline.cmdbuff + ccline.cmdpos);
     while (ccline.cmdpos > 0 && utf_iscomposing(c)) {
       i = utf_head_off(ccline.cmdbuff, ccline.cmdbuff + ccline.cmdpos - 1) + 1;
       ccline.cmdpos -= i;
@@ -3619,7 +3603,7 @@ void put_on_cmdline(const char *str, int len, bool redraw)
 
   if (redraw && !cmd_silent) {
     msg_no_more = true;
-    i = cmdline_row;
+    int i = cmdline_row;
     cursorcmd();
     draw_cmdline(ccline.cmdpos, ccline.cmdlen - ccline.cmdpos);
     // Avoid clearing the rest of the line too often.
@@ -3628,6 +3612,7 @@ void put_on_cmdline(const char *str, int len, bool redraw)
     }
     msg_no_more = false;
   }
+  int m;
   if (KeyTyped) {
     m = Columns * Rows;
     if (m < 0) {            // overflow, Columns or Rows at weird value
@@ -3636,8 +3621,8 @@ void put_on_cmdline(const char *str, int len, bool redraw)
   } else {
     m = MAXCOL;
   }
-  for (i = 0; i < len; i++) {
-    c = cmdline_charsize(ccline.cmdpos);
+  for (int i = 0; i < len; i++) {
+    int c = cmdline_charsize(ccline.cmdpos);
     // count ">" for a double-wide char that doesn't fit.
     correct_screencol(ccline.cmdpos, c, &ccline.cmdspos);
     // Stop cursor at the end of the screen, but do increment the
@@ -3647,9 +3632,7 @@ void put_on_cmdline(const char *str, int len, bool redraw)
       ccline.cmdspos += c;
     }
     c = utfc_ptr2len(ccline.cmdbuff + ccline.cmdpos) - 1;
-    if (c > len - i - 1) {
-      c = len - i - 1;
-    }
+    c = MIN(c, len - i - 1);
     ccline.cmdpos += c;
     i += c;
     ccline.cmdpos++;
@@ -3886,17 +3869,13 @@ void cursorcmd(void)
   }
 
   if (ui_has(kUICmdline)) {
-    if (ccline.redraw_state < kCmdRedrawPos) {
-      ccline.redraw_state = kCmdRedrawPos;
-    }
+    ccline.redraw_state = MAX(ccline.redraw_state, kCmdRedrawPos);
     return;
   }
 
   msg_row = cmdline_row + (ccline.cmdspos / Columns);
   msg_col = ccline.cmdspos % Columns;
-  if (msg_row >= Rows) {
-    msg_row = Rows - 1;
-  }
+  msg_row = MIN(msg_row, Rows - 1);
 
   msg_cursor_goto(msg_row, msg_col);
 }
@@ -4192,11 +4171,7 @@ static int set_cmdline_pos(int pos)
 
   // The position is not set directly but after CTRL-\ e or CTRL-R = has
   // changed the command line.
-  if (pos < 0) {
-    new_cmdpos = 0;
-  } else {
-    new_cmdpos = pos;
-  }
+  new_cmdpos = MAX(0, pos);
 
   return 0;
 }