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)
diff --git a/src/fileio.c b/src/fileio.c
index 6e66a3e..f05abe6 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -261,11 +261,21 @@
 	{
 	    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))