Merge branch 'tl/trace2-config-scope'

Tweak trace2 output about configuration variables.

* tl/trace2-config-scope:
  tr2: shows scope unconditionally in addition to key-value pair
  api-trace2.txt: print config key-value pair

Documentation/technical/api-trace2.txt

@@ -717,6 +717,7 @@ The "exec_id" field is a command-unique id and is only useful if the
 {
 	"event":"def_param",
 	...
+	"scope":"global",
 	"param":"core.abbrev",
 	"value":"7"
 }
@@ -1207,6 +1208,45 @@ at offset 508.
 This example also shows that thread names are assigned in a racy manner
 as each thread starts and allocates TLS storage.
 
+Config (def param) Events::
+
+	  Dump "interesting" config values to trace2 log.
++
+We can optionally emit configuration events, see
+`trace2.configparams` in linkgit:git-config[1] for how to enable
+it.
++
+----------------
+$ git config --system color.ui never
+$ git config --global color.ui always
+$ git config --local color.ui auto
+$ git config --list --show-scope | grep 'color.ui'
+system  color.ui=never
+global  color.ui=always
+local   color.ui=auto
+----------------
++
+Then, mark the config `color.ui` as "interesting" config with
+`GIT_TRACE2_CONFIG_PARAMS`:
++
+----------------
+$ export GIT_TRACE2_PERF_BRIEF=1
+$ export GIT_TRACE2_PERF=~/log.perf
+$ export GIT_TRACE2_CONFIG_PARAMS=color.ui
+$ git version
+...
+$ cat ~/log.perf
+d0 | main                     | version      |     |           |           |              | ...
+d0 | main                     | start        |     |  0.001642 |           |              | /usr/local/bin/git version
+d0 | main                     | cmd_name     |     |           |           |              | version (version)
+d0 | main                     | def_param    |     |           |           | scope:system | color.ui:never
+d0 | main                     | def_param    |     |           |           | scope:global | color.ui:always
+d0 | main                     | def_param    |     |           |           | scope:local  | color.ui:auto
+d0 | main                     | data         | r0  |  0.002100 |  0.002100 | fsync        | fsync/writeout-only:0
+d0 | main                     | data         | r0  |  0.002126 |  0.002126 | fsync        | fsync/hardware-flush:0
+d0 | main                     | exit         |     |  0.000470 |           |              | code:0
+d0 | main                     | atexit       |     |  0.000477 |           |              | code:0
+----------------
 == Future Work
 
 === Relationship to the Existing Trace Api (api-trace.txt)

trace2/tr2_tgt_event.c

@@ -479,9 +479,12 @@ static void fn_param_fl(const char *file, int line, const char *param,
 {
 	const char *event_name = "def_param";
 	struct json_writer jw = JSON_WRITER_INIT;
+	enum config_scope scope = current_config_scope();
+	const char *scope_name = config_scope_name(scope);
 
 	jw_object_begin(&jw, 0);
 	event_fmt_prepare(event_name, file, line, NULL, &jw);
+	jw_object_string(&jw, "scope", scope_name);
 	jw_object_string(&jw, "param", param);
 	jw_object_string(&jw, "value", value);
 	jw_end(&jw);

trace2/tr2_tgt_normal.c

@@ -298,8 +298,11 @@ static void fn_param_fl(const char *file, int line, const char *param,
 			const char *value)
 {
 	struct strbuf buf_payload = STRBUF_INIT;
+	enum config_scope scope = current_config_scope();
+	const char *scope_name = config_scope_name(scope);
 
-	strbuf_addf(&buf_payload, "def_param %s=%s", param, value);
+	strbuf_addf(&buf_payload, "def_param scope:%s %s=%s", scope_name, param,
+		    value);
 	normal_io_write_fl(file, line, &buf_payload);
 	strbuf_release(&buf_payload);
 }

trace2/tr2_tgt_perf.c

@@ -441,12 +441,17 @@ static void fn_param_fl(const char *file, int line, const char *param,
 {
 	const char *event_name = "def_param";
 	struct strbuf buf_payload = STRBUF_INIT;
+	struct strbuf scope_payload = STRBUF_INIT;
+	enum config_scope scope = current_config_scope();
+	const char *scope_name = config_scope_name(scope);
 
 	strbuf_addf(&buf_payload, "%s:%s", param, value);
+	strbuf_addf(&scope_payload, "%s:%s", "scope", scope_name);
 
-	perf_io_write_fl(file, line, event_name, NULL, NULL, NULL, NULL,
-			 &buf_payload);
+	perf_io_write_fl(file, line, event_name, NULL, NULL, NULL,
+			 scope_payload.buf, &buf_payload);
 	strbuf_release(&buf_payload);
+	strbuf_release(&scope_payload);
 }
 
 static void fn_repo_fl(const char *file, int line,