nmcli: fix bash completion for fields

The code handling options with supposes, that options
are split by `=`, which is not the case. This fixes the following:

```
nmcli -f ipv4.ad\t\t
nmcli -f ipv4.ad=ipv4.addresses

nmcli --field ipv4.ad\t\t
nmcli --field ipv4.ad=ipv4.addresses
```

Using options with values separated with `=` remains broken,
but this change doesn't affect it:

```
nmcli --field=ipv4.ad\t\t
nmcli --field=ipv4.ad
```

Also, `man` and `usage` uses `--color auto|yes|no`,
not `--color=auto|yes|no`. So, this fix should be sufficient.

Bug report:
https://bugzilla.redhat.com/show_bug.cgi?id=2115827

src/nmcli/nmcli.c

@@ -163,17 +163,18 @@ complete_one(gpointer key, gpointer value, gpointer user_data)
         last = prefix;
 
     if ((!*last && !strchr(name, '.')) || matches(last, name)) {
-        if (option != prefix) {
+        if (!nm_streq0(option, prefix)) {
             /* value prefix was not a standalone argument,
              * it was part of --option=<value> argument.
              * Repeat the part leading to "=". */
-            nmc_print("%s=", option);
+            nmc_print("%s\n", option);
+        } else {
+            nmc_print("%.*s%s%s\n",
+                      (int) (last - prefix),
+                      prefix,
+                      name,
+                      nm_streq(last, name) ? "," : "");
         }
-        nmc_print("%.*s%s%s\n",
-                  (int) (last - prefix),
-                  prefix,
-                  name,
-                  strcmp(last, name) == 0 ? "," : "");
     }
 }
 
@@ -225,13 +226,14 @@ complete_option_with_value(const char *option, const char *prefix, ...)
     va_start(args, prefix);
     while ((candidate = va_arg(args, const char *))) {
         if (!*prefix || matches(prefix, candidate)) {
-            if (option != prefix) {
+            if (!nm_streq0(option, prefix)) {
                 /* value prefix was not a standalone argument,
                  * it was part of --option=<value> argument.
                  * Repeat the part leading to "=". */
-                nmc_print("%s=", option);
+                nmc_print("%s%s\n", option, candidate + strlen(prefix));
+            } else {
+                nmc_print("%s\n", candidate);
             }
-            nmc_print("%s\n", candidate);
         }
     }
     va_end(args);