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;

```

1 files changed, 9 insertions, 25 deletions

diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index ed5c9a508c..c403e94184 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -1132,17 +1132,11 @@ static void serialize_pos(bufinfo_T *bi, pos_T pos)
 static void unserialize_pos(bufinfo_T *bi, pos_T *pos)
 {
   pos->lnum = undo_read_4c(bi);
-  if (pos->lnum < 0) {
-    pos->lnum = 0;
-  }
+  pos->lnum = MAX(pos->lnum, 0);
   pos->col = undo_read_4c(bi);
-  if (pos->col < 0) {
-    pos->col = 0;
-  }
+  pos->col = MAX(pos->col, 0);
   pos->coladd = undo_read_4c(bi);
-  if (pos->coladd < 0) {
-    pos->coladd = 0;
-  }
+  pos->coladd = MAX(pos->coladd, 0);
 }
 
 /// Serializes "info".
@@ -1209,14 +1203,12 @@ void u_write_undo(const char *const name, const bool forceit, buf_T *const buf,
   // Strip any sticky and executable bits.
   perm = perm & 0666;
 
-  int fd;
-
   // If the undo file already exists, verify that it actually is an undo
   // file, and delete it.
   if (os_path_exists(file_name)) {
     if (name == NULL || !forceit) {
       // Check we can read it and it's an undo file.
-      fd = os_open(file_name, O_RDONLY, 0);
+      int fd = os_open(file_name, O_RDONLY, 0);
       if (fd < 0) {
         if (name != NULL || p_verbose > 0) {
           if (name == NULL) {
@@ -1261,7 +1253,7 @@ void u_write_undo(const char *const name, const bool forceit, buf_T *const buf,
     goto theend;
   }
 
-  fd = os_open(file_name, O_CREAT|O_WRONLY|O_EXCL|O_NOFOLLOW, perm);
+  int fd = os_open(file_name, O_CREAT|O_WRONLY|O_EXCL|O_NOFOLLOW, perm);
   if (fd < 0) {
     semsg(_(e_not_open), file_name);
     goto theend;
@@ -2001,9 +1993,7 @@ void undo_time(int step, bool sec, bool file, bool absolute)
       target = curbuf->b_u_seq_cur + step;
     }
     if (step < 0) {
-      if (target < 0) {
-        target = 0;
-      }
+      target = MAX(target, 0);
       closest = -1;
     } else {
       if (dosec) {
@@ -2396,9 +2386,7 @@ static void u_undoredo(bool undo, bool do_buf_event)
     }
 
     // Set the '[ mark.
-    if (top + 1 < curbuf->b_op_start.lnum) {
-      curbuf->b_op_start.lnum = top + 1;
-    }
+    curbuf->b_op_start.lnum = MIN(curbuf->b_op_start.lnum, top + 1);
     // Set the '] mark.
     if (newsize == 0 && top + 1 > curbuf->b_op_end.lnum) {
       curbuf->b_op_end.lnum = top + 1;
@@ -2419,12 +2407,8 @@ static void u_undoredo(bool undo, bool do_buf_event)
   }
 
   // Ensure the '[ and '] marks are within bounds.
-  if (curbuf->b_op_start.lnum > curbuf->b_ml.ml_line_count) {
-    curbuf->b_op_start.lnum = curbuf->b_ml.ml_line_count;
-  }
-  if (curbuf->b_op_end.lnum > curbuf->b_ml.ml_line_count) {
-    curbuf->b_op_end.lnum = curbuf->b_ml.ml_line_count;
-  }
+  curbuf->b_op_start.lnum = MIN(curbuf->b_op_start.lnum, curbuf->b_ml.ml_line_count);
+  curbuf->b_op_end.lnum = MIN(curbuf->b_op_end.lnum, curbuf->b_ml.ml_line_count);
 
   // Adjust Extmarks
   if (undo) {