[PATCH v7 7/7] tr2: dump names if config exist in multiple scopes

[Teng Long <dyroneteng@gmail.com>]

When we specify GIT_TRACE2_CONFIG_PARAMS or trace2.configparams,
trace2 will prints "interesting" config values to log. Sometimes,
when a config set in multiple scope files, the following output
looks like (the irrelevant fields are omitted here as "..."):

...| def_param    |  ...  | core.multipackindex:false
...| def_param    |  ...  | core.multipackindex:false
...| def_param    |  ...  | core.multipackindex:false

As the log shows, even each config in different scope is dumped, but
we don't know which scope it comes from. Therefore, it's better to
add the scope names as well to make them be more recognizable. For
example, when execute:

    $ GIT_TRACE2_PERF=1 \
    > GIT_TRACE2_CONFIG_PARAMS=core.multipackIndex \
    > git rev-list --test-bitmap HEAD"

The following is the ouput (the irrelevant fields are omitted here
as "..."):

Format normal:
... git.c:461 ... def_param scope:system core.multipackindex=false
... git.c:461 ... def_param scope:global core.multipackindex=false
... git.c:461 ... def_param scope:local core.multipackindex=false

Format perf:

... | def_param    | ... | scope:system | core.multipackindex:false
... | def_param    | ... | scope:global | core.multipackindex:false
... | def_param    | ... | scope:local  | core.multipackindex:false

Format event:

{"event":"def_param", ... ,"scope":"system","param":"core.multipackindex","value":"false"}
{"event":"def_param", ... ,"scope":"global","param":"core.multipackindex","value":"false"}
{"event":"def_param", ... ,"scope":"local","param":"core.multipackindex","value":"false"}

Signed-off-by: Teng Long <dyroneteng@gmail.com>
---
 Documentation/technical/api-trace2.txt | 45 ++++++++++++++++++++++++++
 trace2/tr2_tgt_event.c                 |  3 ++
 trace2/tr2_tgt_normal.c                |  5 ++-
 trace2/tr2_tgt_perf.c                  |  9 ++++--
 4 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index bb13ca3db8..48205a5ac5 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -1207,6 +1207,51 @@ at offset 508.
 This example also shows that thread names are assigned in a racy manner
 as each thread starts and allocates TLS storage.
 
+Print Configs::
+
+	  Dump "interesting" config values to trace2 log.
++
+The environment variable `GIT_TRACE2_CONFIG_PARAMS` and configuration
+`trace2.configparams` can be used to output config values which you care
+about. For example, assume that we want to config different `color.ui`
+values in multiple scopes, such as:
++
+----------------
+$ 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        |     |  0.000284 |           |              | /opt/git/master/bin/git version
+d0 | main                     | cmd_ancestry |     |           |           |              | ancestry:[bash sshd sshd sshd systemd]
+d0 | main                     | cmd_name     |     |           |           |              | version (version)
+d0 | main                     | exit         |     |  0.000419 |           |              | code:0
+d0 | main                     | atexit       |     |  0.000426 |           |              | code:0
+d0 | main                     | version      |     |           |           |              | ...
+d0 | main                     | start        |     |  0.000275 |           |              | /opt/git/master/bin/git version
+d0 | main                     | cmd_ancestry |     |           |           |              | ancestry:[bash sshd sshd sshd systemd]
+d0 | main                     | cmd_name     |     |           |           |              | version (version)
+d0 | main                     | def_param    |     |           |           |              | color.ui:never
+d0 | main                     | def_param    |     |           |           |              | color.ui:always
+d0 | main                     | def_param    |     |           |           |              | color.ui:auto
+d0 | main                     | exit         |     |  0.000543 |           |              | code:0
+d0 | main                     | atexit       |     |  0.000549 |           |              | code:0
+----------------
 == Future Work
 
 === Relationship to the Existing Trace Api (api-trace.txt)
diff --git a/trace2/tr2_tgt_event.c b/trace2/tr2_tgt_event.c
index c5c8cfbbaa..37a3163be1 100644
--- a/trace2/tr2_tgt_event.c
+++ b/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);
diff --git a/trace2/tr2_tgt_normal.c b/trace2/tr2_tgt_normal.c
index c42fbade7f..69f8033077 100644
--- a/trace2/tr2_tgt_normal.c
+++ b/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);
 }
diff --git a/trace2/tr2_tgt_perf.c b/trace2/tr2_tgt_perf.c
index a1eff8bea3..8cb792488c 100644
--- a/trace2/tr2_tgt_perf.c
+++ b/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,
-- 
2.35.0.rc0.679.gc613175da2