vim-patch:8.2.2468: not easy to get the full command name from a shortened one

Problem:    Not easy to get the full command name from a shortened one.
Solution:   Add fullcommand(). (Martin Tournoij, closes vim/vim#7777)
https://github.com/vim/vim/commit/038e09ee7645731de0296d255aabb17603276443

4 files changed, 64 insertions, 0 deletions

diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index 9507a12a02..e445a08227 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -133,6 +133,7 @@ return {
     foldtext={},
     foldtextresult={args=1, base=1},
     foreground={},
+    fullcommand={args=1, base=1},
     funcref={args={1, 3}, base=1},
     ['function']={args={1, 3}, base=1},
     garbagecollect={args={0, 1}},
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index ee7946fe3e..61686b48f0 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -2900,6 +2900,31 @@ int cmd_exists(const char *const name)
   return ea.cmdidx == CMD_SIZE ? 0 : (full ? 2 : 1);
 }
 
+// "fullcommand" function
+void f_fullcommand(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  exarg_T ea;
+  char_u *name = argvars[0].vval.v_string;
+
+  while (name[0] != NUL && name[0] == ':') {
+    name++;
+  }
+  name = skip_range(name, NULL);
+
+  rettv->v_type = VAR_STRING;
+
+  ea.cmd = (*name == '2' || *name == '3') ? name + 1 : name;
+  ea.cmdidx = (cmdidx_T)0;
+  char_u *p = find_command(&ea, NULL);
+  if (p == NULL || ea.cmdidx == CMD_SIZE) {
+    return;
+  }
+
+  rettv->vval.v_string = vim_strsave(ea.cmdidx < 0
+                                     ? get_user_commands(NULL, ea.useridx)
+                                     : cmdnames[ea.cmdidx].cmd_name);
+}
+
 /// This is all pretty much copied from do_one_cmd(), with all the extra stuff
 /// we don't need/want deleted.  Maybe this could be done better if we didn't
 /// repeat all this stuff.  The only problem is that they may not stay
diff --git a/src/nvim/ex_docmd.h b/src/nvim/ex_docmd.h
index 7ec4fad277..a302d4a3c5 100644
--- a/src/nvim/ex_docmd.h
+++ b/src/nvim/ex_docmd.h
@@ -2,6 +2,7 @@
 #define NVIM_EX_DOCMD_H
 
 #include "nvim/ex_cmds_defs.h"
+#include "nvim/eval/funcs.h"
 #include "nvim/globals.h"
 
 // flags for do_cmdline()
diff --git a/src/nvim/testdir/test_cmdline.vim b/src/nvim/testdir/test_cmdline.vim
index 49a5386337..1672b0e840 100644
--- a/src/nvim/testdir/test_cmdline.vim
+++ b/src/nvim/testdir/test_cmdline.vim
@@ -467,6 +467,43 @@ func Test_getcompletion()
   call assert_fails('call getcompletion("abc", [])', 'E475:')
 endfunc
 
+func Test_fullcommand()
+  let tests = {
+        \ '':           '',
+        \ ':':          '',
+        \ ':::':        '',
+        \ ':::5':       '',
+        \ 'not_a_cmd':  '',
+        \ 'Check':      '',
+        \ 'syntax':     'syntax',
+        \ ':syntax':    'syntax',
+        \ '::::syntax': 'syntax',
+        \ 'sy':         'syntax',
+        \ 'syn':        'syntax',
+        \ 'synt':       'syntax',
+        \ ':sy':        'syntax',
+        \ '::::sy':     'syntax',
+        \ 'match':      'match',
+        \ '2match':     'match',
+        \ '3match':     'match',
+        \ 'aboveleft':  'aboveleft',
+        \ 'abo':        'aboveleft',
+        \ 's':          'substitute',
+        \ '5s':         'substitute',
+        \ ':5s':        'substitute',
+        \ "'<,'>s":     'substitute',
+        \ ":'<,'>s":    'substitute',
+        \ 'CheckUni':   'CheckUnix',
+        \ 'CheckUnix':  'CheckUnix',
+  \ }
+
+  for [in, want] in items(tests)
+    call assert_equal(want, fullcommand(in))
+  endfor
+
+  call assert_equal('syntax', 'syn'->fullcommand())
+endfunc
+
 func Test_shellcmd_completion()
   let save_path = $PATH