DisableFlagParsing must disable flag completion (#1161)

When a command has set DisableFlagParsing=true, it means Cobra should
not be handling flags for that command but should let the command
handle them itself.  In fact, Cobra normally won't have been told at all
about flags for this command.

Not knowing about the flags of the command also implies that Cobra
cannot perform flag completion as it does not have the necessary info.

This commit still tries to do flag name completion, but when
DisableFlagParsing==true, it continues on so that ValidArgsFunction will
be called; this allows the program to handle completion for its own
flags when DisableFlagParsing==true.

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

bash_completions.go

@@ -193,7 +193,13 @@ __%[1]s_handle_reply()
                     fi
                 fi
             fi
-            return 0;
+
+            if [[ -z "${flag_parsing_disabled}" ]]; then
+                # If flag parsing is enabled, we have completed the flags and can return.
+                # If flag parsing is disabled, we may not know all (or any) of the flags, so we fallthrough
+                # to possibly call handle_go_custom_completion.
+                return 0;
+            fi
             ;;
     esac
 
@@ -394,6 +400,7 @@ func writePostscript(buf io.StringWriter, name string) {
     fi
 
     local c=0
+    local flag_parsing_disabled=
     local flags=()
     local two_word_flags=()
     local local_nonpersistent_flags=()
@@ -535,6 +542,11 @@ func writeFlags(buf io.StringWriter, cmd *Command) {
     flags_completion=()
 
 `)
+
+	if cmd.DisableFlagParsing {
+		WriteStringAndCheck(buf, "    flag_parsing_disabled=1\n")
+	}
+
 	localNonPersistentFlags := cmd.LocalNonPersistentFlags()
 	cmd.NonInheritedFlags().VisitAll(func(flag *pflag.Flag) {
 		if nonCompletableFlag(flag) {