vim-patch:9.1.1224: cannot :put while keeping indent (#33076)

Problem:  cannot :put while keeping indent (Peter Aronoff)
Solution: add the :iput ex command (64-bitman)

fixes: vim/vim#16225
closes: vim/vim#16886

https://github.com/vim/vim/commit/e08f10a55c3f15b0b4af631908551d88ec4fe502

Cherry-pick test_put.vim changes from patch 8.2.1593.

N/A patches:
vim-patch:9.1.1213: cannot :put while keeping indent
vim-patch:9.1.1215: Patch 9.1.1213 has some issues

Co-authored-by: 64-bitman <60551350+64-bitman@users.noreply.github.com>
Co-authored-by: Hirohito Higashi <h.east.727@gmail.com>

3 files changed, 28 insertions, 5 deletions

diff --git a/src/nvim/api/command.c b/src/nvim/api/command.c
index de83ff97f7..4b93f09c61 100644
--- a/src/nvim/api/command.c
+++ b/src/nvim/api/command.c
@@ -504,7 +504,9 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Arena
     VALIDATE((regname != '='), "%s", "Cannot use register \"=", {
       goto end;
     });
-    VALIDATE(valid_yank_reg(regname, ea.cmdidx != CMD_put && !IS_USER_CMDIDX(ea.cmdidx)),
+    VALIDATE(valid_yank_reg(regname,
+                            (!IS_USER_CMDIDX(ea.cmdidx)
+                             && ea.cmdidx != CMD_put && ea.cmdidx != CMD_iput)),
              "Invalid register: \"%c", regname, {
       goto end;
     });
diff --git a/src/nvim/ex_cmds.lua b/src/nvim/ex_cmds.lua
index d68d5a9afa..34723b6102 100644
--- a/src/nvim/ex_cmds.lua
+++ b/src/nvim/ex_cmds.lua
@@ -1219,6 +1219,12 @@ M.cmds = {
     func = 'ex_intro',
   },
   {
+    command = 'iput',
+    flags = bit.bor(RANGE, WHOLEFOLD, BANG, REGSTR, TRLBAR, ZEROR, CMDWIN, LOCK_OK, MODIFY),
+    addr_type = 'ADDR_LINES',
+    func = 'ex_iput',
+  },
+  {
     command = 'isearch',
     flags = bit.bor(BANG, RANGE, DFLALL, WHOLEFOLD, EXTRA, CMDWIN, LOCK_OK),
     addr_type = 'ADDR_LINES',
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 640c729e3b..6c5cca5d5c 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -1393,8 +1393,9 @@ static void parse_register(exarg_T *eap)
       // Do not allow register = for user commands
       && (!IS_USER_CMDIDX(eap->cmdidx) || *eap->arg != '=')
       && !((eap->argt & EX_COUNT) && ascii_isdigit(*eap->arg))) {
-    if (valid_yank_reg(*eap->arg, (eap->cmdidx != CMD_put
-                                   && !IS_USER_CMDIDX(eap->cmdidx)))) {
+    if (valid_yank_reg(*eap->arg,
+                       (!IS_USER_CMDIDX(eap->cmdidx)
+                        && eap->cmdidx != CMD_put && eap->cmdidx != CMD_iput))) {
       eap->regname = (uint8_t)(*eap->arg++);
       // for '=' register: accept the rest of the line as an expression
       if (eap->arg[-1] == '=' && eap->arg[0] != NUL) {
@@ -1752,7 +1753,7 @@ int execute_cmd(exarg_T *eap, CmdParseInfo *cmdinfo, bool preview)
 
   if (!MODIFIABLE(curbuf) && (eap->argt & EX_MODIFY)
       // allow :put in terminals
-      && !(curbuf->terminal && eap->cmdidx == CMD_put)) {
+      && !(curbuf->terminal && (eap->cmdidx == CMD_put || eap->cmdidx == CMD_iput))) {
     errormsg = _(e_modifiable);
     goto end;
   }
@@ -2155,7 +2156,7 @@ static char *do_one_cmd(char **cmdlinep, int flags, cstack_T *cstack, LineGetter
     }
     if (!MODIFIABLE(curbuf) && (ea.argt & EX_MODIFY)
         // allow :put in terminals
-        && (!curbuf->terminal || ea.cmdidx != CMD_put)) {
+        && !(curbuf->terminal && (ea.cmdidx == CMD_put || ea.cmdidx == CMD_iput))) {
       // Command not allowed in non-'modifiable' buffer
       errormsg = _(e_modifiable);
       goto doend;
@@ -6306,6 +6307,20 @@ static void ex_put(exarg_T *eap)
          PUT_LINE|PUT_CURSLINE);
 }
 
+/// ":iput".
+static void ex_iput(exarg_T *eap)
+{
+  // ":0iput" works like ":1iput!".
+  if (eap->line2 == 0) {
+    eap->line2 = 1;
+    eap->forceit = true;
+  }
+  curwin->w_cursor.lnum = eap->line2;
+  check_cursor_col(curwin);
+  do_put(eap->regname, NULL, eap->forceit ? BACKWARD : FORWARD, 1L,
+         PUT_LINE|PUT_CURSLINE|PUT_FIXINDENT);
+}
+
 /// Handle ":copy" and ":move".
 static void ex_copymove(exarg_T *eap)
 {