vim-patch:9.0.1158: code is indented more than necessary (#21697)

Problem:    Code is indented more than necessary.
Solution:   Use an early return where it makes sense. (Yegappan Lakshmanan,
            closes vim/vim#11787)

https://github.com/vim/vim/commit/7f8b2559a30e2e2a443c35b28e94c6b45ba7ae04

Omit reset_last_used_map(): only used in Vim9 script.

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

3 files changed, 81 insertions, 57 deletions

diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index 47f2e44c39..32d7c52749 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -1150,10 +1150,12 @@ static void ff_push(ff_search_ctx_T *search_ctx, ff_stack_T *stack_ptr)
 {
   // check for NULL pointer, not to return an error to the user, but
   // to prevent a crash
-  if (stack_ptr != NULL) {
-    stack_ptr->ffs_prev = search_ctx->ffsc_stack_ptr;
-    search_ctx->ffsc_stack_ptr = stack_ptr;
+  if (stack_ptr == NULL) {
+    return;
   }
+
+  stack_ptr->ffs_prev = search_ctx->ffsc_stack_ptr;
+  search_ctx->ffsc_stack_ptr = stack_ptr;
 }
 
 /// Pop a dir from the directory stack.
diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index 6d85206d18..8b773b2eee 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -477,12 +477,15 @@ static void newFoldLevelWin(win_T *wp)
 /// Apply 'foldlevel' to all folds that don't contain the cursor.
 void foldCheckClose(void)
 {
-  if (*p_fcl != NUL) {  // can only be "all" right now
-    checkupdate(curwin);
-    if (checkCloseRec(&curwin->w_folds, curwin->w_cursor.lnum,
-                      (int)curwin->w_p_fdl)) {
-      changed_window_setting();
-    }
+  if (*p_fcl == NUL) {
+    return;
+  }
+
+  // can only be "all" right now
+  checkupdate(curwin);
+  if (checkCloseRec(&curwin->w_folds, curwin->w_cursor.lnum,
+                    (int)curwin->w_p_fdl)) {
+    changed_window_setting();
   }
 }
 
@@ -1005,15 +1008,18 @@ void foldAdjustVisual(void)
   if (hasFolding(start->lnum, &start->lnum, NULL)) {
     start->col = 0;
   }
-  if (hasFolding(end->lnum, NULL, &end->lnum)) {
-    ptr = ml_get(end->lnum);
-    end->col = (colnr_T)strlen(ptr);
-    if (end->col > 0 && *p_sel == 'o') {
-      end->col--;
-    }
-    // prevent cursor from moving on the trail byte
-    mb_adjust_cursor();
+
+  if (!hasFolding(end->lnum, NULL, &end->lnum)) {
+    return;
+  }
+
+  ptr = ml_get(end->lnum);
+  end->col = (colnr_T)strlen(ptr);
+  if (end->col > 0 && *p_sel == 'o') {
+    end->col--;
   }
+  // prevent cursor from moving on the trail byte
+  mb_adjust_cursor();
 }
 
 // cursor_foldstart() {{{2
@@ -1115,10 +1121,12 @@ static int foldLevelWin(win_T *wp, linenr_T lnum)
 /// Check if the folds in window "wp" are invalid and update them if needed.
 static void checkupdate(win_T *wp)
 {
-  if (wp->w_foldinvalid) {
-    foldUpdate(wp, (linenr_T)1, (linenr_T)MAXLNUM);     // will update all
-    wp->w_foldinvalid = false;
+  if (!wp->w_foldinvalid) {
+    return;
   }
+
+  foldUpdate(wp, (linenr_T)1, (linenr_T)MAXLNUM);     // will update all
+  wp->w_foldinvalid = false;
 }
 
 // setFoldRepeat() {{{2
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index b0dac7aea6..1beabb6111 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -272,10 +272,12 @@ static void delete_buff_tail(buffheader_T *buf, int slen)
     return;  // nothing to delete
   }
   len = (int)strlen(buf->bh_curr->b_str);
-  if (len >= slen) {
-    buf->bh_curr->b_str[len - slen] = NUL;
-    buf->bh_space += (size_t)slen;
+  if (len < slen) {
+    return;
   }
+
+  buf->bh_curr->b_str[len - slen] = NUL;
+  buf->bh_space += (size_t)slen;
 }
 
 /// Add number "n" to buffer "buf".
@@ -439,24 +441,28 @@ void beep_flush(void)
 // This is used for the CTRL-O <.> command in insert mode.
 void ResetRedobuff(void)
 {
-  if (!block_redo) {
-    free_buff(&old_redobuff);
-    old_redobuff = redobuff;
-    redobuff.bh_first.b_next = NULL;
+  if (block_redo) {
+    return;
   }
+
+  free_buff(&old_redobuff);
+  old_redobuff = redobuff;
+  redobuff.bh_first.b_next = NULL;
 }
 
 // Discard the contents of the redo buffer and restore the previous redo
 // buffer.
 void CancelRedo(void)
 {
-  if (!block_redo) {
-    free_buff(&redobuff);
-    redobuff = old_redobuff;
-    old_redobuff.bh_first.b_next = NULL;
-    start_stuff();
-    while (read_readbuffers(true) != NUL) {}
+  if (block_redo) {
+    return;
   }
+
+  free_buff(&redobuff);
+  redobuff = old_redobuff;
+  old_redobuff.bh_first.b_next = NULL;
+  start_stuff();
+  while (read_readbuffers(true) != NUL) {}
 }
 
 /// Save redobuff and old_redobuff to save_redobuff and save_old_redobuff.
@@ -470,10 +476,12 @@ void saveRedobuff(save_redo_T *save_redo)
 
   // Make a copy, so that ":normal ." in a function works.
   char *const s = (char *)get_buffcont(&save_redo->sr_redobuff, false);
-  if (s != NULL) {
-    add_buff(&redobuff, s, -1L);
-    xfree(s);
+  if (s == NULL) {
+    return;
   }
+
+  add_buff(&redobuff, s, -1L);
+  xfree(s);
 }
 
 /// Restore redobuff and old_redobuff from save_redobuff and save_old_redobuff.
@@ -811,14 +819,16 @@ void stop_redo_ins(void)
 // be impossible to type anything.
 static void init_typebuf(void)
 {
-  if (typebuf.tb_buf == NULL) {
-    typebuf.tb_buf = typebuf_init;
-    typebuf.tb_noremap = noremapbuf_init;
-    typebuf.tb_buflen = TYPELEN_INIT;
-    typebuf.tb_len = 0;
-    typebuf.tb_off = MAXMAPLEN + 4;
-    typebuf.tb_change_cnt = 1;
+  if (typebuf.tb_buf != NULL) {
+    return;
   }
+
+  typebuf.tb_buf = typebuf_init;
+  typebuf.tb_noremap = noremapbuf_init;
+  typebuf.tb_buflen = TYPELEN_INIT;
+  typebuf.tb_len = 0;
+  typebuf.tb_off = MAXMAPLEN + 4;
+  typebuf.tb_change_cnt = 1;
 }
 
 /// @return true when keys cannot be remapped.
@@ -1126,10 +1136,12 @@ static void gotchars(const char_u *chars, size_t len)
 /// Only affects recorded characters.
 void ungetchars(int len)
 {
-  if (reg_recording != 0) {
-    delete_buff_tail(&recordbuff, len);
-    last_recorded_len -= (size_t)len;
+  if (reg_recording == 0) {
+    return;
   }
+
+  delete_buff_tail(&recordbuff, len);
+  last_recorded_len -= (size_t)len;
 }
 
 // Sync undo.  Called when typed characters are obtained from the typeahead
@@ -1775,19 +1787,21 @@ void f_getcharstr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   getchar_common(argvars, rettv);
 
-  if (rettv->v_type == VAR_NUMBER) {
-    char temp[7];   // mbyte-char: 6, NUL: 1
-    const varnumber_T n = rettv->vval.v_number;
-    int i = 0;
+  if (rettv->v_type != VAR_NUMBER) {
+    return;
+  }
 
-    if (n != 0) {
-      i += utf_char2bytes((int)n, (char *)temp);
-    }
-    assert(i < 7);
-    temp[i++] = NUL;
-    rettv->v_type = VAR_STRING;
-    rettv->vval.v_string = xstrdup(temp);
+  char temp[7];   // mbyte-char: 6, NUL: 1
+  const varnumber_T n = rettv->vval.v_number;
+  int i = 0;
+
+  if (n != 0) {
+    i += utf_char2bytes((int)n, (char *)temp);
   }
+  assert(i < 7);
+  temp[i++] = NUL;
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = xstrdup(temp);
 }
 
 /// "getcharmod()" function