[PATCH v2] perf list: For metricgroup only list include description

[Ian Rogers <irogers@google.com>]

If perf list is invoked with 'metricgroups' include the description
unless it is invoked with flags to exclude it. Make the description of
metricgroup dumping dependent on the desc flag in print_state as with
metrics.

Before:
```
$ perf list metricgroups
List of pre-defined events (to be used in -e or -M):

Metric Groups:

Backend
Bad
BadSpec
...
```

After:
```
$ perf list metricgroups
List of pre-defined events (to be used in -e or -M):

Metric Groups:

Backend [Grouping from Top-down Microarchitecture Analysis Metrics spreadsheet]
Bad [Grouping from Top-down Microarchitecture Analysis Metrics spreadsheet]
BadSpec
...
```

Signed-off-by: Ian Rogers <irogers@google.com>
---
v2 rebases on top of perf-tools-next patch:
79bacb6ad73c perf list: Add output file option
https://lore.kernel.org/r/20240124043015.1388867-3-irogers@google.com
---
 tools/perf/builtin-list.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
index e27a1b1288c2..02bf608d585e 100644
--- a/tools/perf/builtin-list.c
+++ b/tools/perf/builtin-list.c
@@ -208,17 +208,24 @@ static void default_print_metric(void *ps,
 	if (!print_state->last_metricgroups ||
 	    strcmp(print_state->last_metricgroups, group ?: "")) {
 		if (group && print_state->metricgroups) {
-			if (print_state->name_only)
+			if (print_state->name_only) {
 				fprintf(fp, "%s ", group);
-			else if (print_state->metrics) {
-				const char *gdesc = describe_metricgroup(group);
+			} else {
+				const char *gdesc = print_state->desc
+					? describe_metricgroup(group)
+					: NULL;
+				const char *print_colon = "";
+
+				if (print_state->metrics) {
+					print_colon = ":";
+					fputc('\n', fp);
+				}
 
 				if (gdesc)
-					fprintf(fp, "\n%s: [%s]\n", group, gdesc);
+					fprintf(fp, "%s%s [%s]\n", group, print_colon, gdesc);
 				else
-					fprintf(fp, "\n%s:\n", group);
-			} else
-				fprintf(fp, "%s\n", group);
+					fprintf(fp, "%s%s\n", group, print_colon);
+			}
 		}
 		zfree(&print_state->last_metricgroups);
 		print_state->last_metricgroups = strdup(group ?: "");
-- 
2.44.0.rc0.258.g7320e95886-goog