patch 8.2.0474: cannot use :write when using a plugin with BufWriteCmd

Problem:    Cannot use :write when using a plugin with BufWriteCmd.
Solution:   Reset BF_NOTEDITED after BufWriteCmd. (closes #5807)

src/fileio.c

@@ -261,11 +261,21 @@ readfile(
 	{
 	    if (apply_autocmds_exarg(EVENT_BUFREADCMD, NULL, sfname,
 							  FALSE, curbuf, eap))
+	    {
+		int status = OK;
 #ifdef FEAT_EVAL
-		return aborting() ? FAIL : OK;
-#else
-		return OK;
+		if (aborting())
+		    status = FAIL;
 #endif
+		// The BufReadCmd code usually uses ":read" to get the text and
+		// perhaps ":file" to change the buffer name. But we should
+		// consider this to work like ":edit", thus reset the
+		// BF_NOTEDITED flag.  Then ":write" will work to overwrite the
+		// same file.
+		if (status == OK)
+		    curbuf->b_flags &= ~BF_NOTEDITED;
+		return status;
+	    }
 	}
 	else if (apply_autocmds_exarg(EVENT_FILEREADCMD, sfname, sfname,
 							    FALSE, NULL, eap))

src/testdir/test_autocmd.vim

@@ -1536,6 +1536,40 @@ func Test_Cmd_Autocmds()
   enew!
 endfunc
 
+func s:ReadFile()
+  setl noswapfile nomodified
+  let filename = resolve(expand("<afile>:p"))
+  execute 'read' fnameescape(filename)
+  1d_
+  exe 'file' fnameescape(filename)
+  setl buftype=acwrite
+endfunc
+
+func s:WriteFile()
+  let filename = resolve(expand("<afile>:p"))
+  setl buftype=
+  noautocmd execute 'write' fnameescape(filename)
+  setl buftype=acwrite
+  setl nomodified
+endfunc
+
+func Test_BufReadCmd()
+  autocmd BufReadCmd *.test call s:ReadFile()
+  autocmd BufWriteCmd *.test call s:WriteFile()
+
+  call writefile(['one', 'two', 'three'], 'Xcmd.test')
+  edit Xcmd.test
+  call assert_match('Xcmd.test" line 1 of 3', execute('file'))
+  normal! Gofour
+  write
+  call assert_equal(['one', 'two', 'three', 'four'], readfile('Xcmd.test'))
+
+  bwipe!
+  call delete('Xcmd.test')
+  au! BufReadCmd
+  au! BufWriteCmd
+endfunc
+
 func SetChangeMarks(start, end)
   exe a:start. 'mark ['
   exe a:end. 'mark ]'

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    474,
 /**/
     473,
 /**/