trace2: update docs to describe system/global config settings

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 152 insertions, 67 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index d87846faa6..7e2a6f61f5 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -422,6 +422,8 @@ include::config/submodule.txt[]
 
 include::config/tag.txt[]
 
+include::config/trace2.txt[]
+
 include::config/transfer.txt[]
 
 include::config/uploadarchive.txt[]
diff --git a/Documentation/config/trace2.txt b/Documentation/config/trace2.txt
new file mode 100644
index 0000000000..a5f409c1c1
--- /dev/null
+++ b/Documentation/config/trace2.txt
@@ -0,0 +1,56 @@
+Trace2 config settings are only read from the system and global
+config files; repository local and worktree config files and `-c`
+command line arguments are not respected.
+
+trace2.normalTarget::
+	This variable controls the normal target destination.
+	It may be overridden by the `GIT_TR2` environment variable.
+	The following table shows possible values.
+
+trace2.perfTarget::
+	This variable controls the performance target destination.
+	It may be overridden by the `GIT_TR2_PERF` environment variable.
+	The following table shows possible values.
+
+trace2.eventTarget::
+	This variable controls the event target destination.
+	It may be overridden by the `GIT_TR2_EVENT` environment variable.
+	The following table shows possible values.
++
+include::../trace2-target-values.txt[]
+
+trace2.normalBrief::
+	Boolean.  When true `time`, `filename`, and `line` fields are
+	omitted from normal output.  May be overridden by the
+	`GIT_TR2_BRIEF` environment variable.  Defaults to false.
+
+trace2.perfBrief::
+	Boolean.  When true `time`, `filename`, and `line` fields are
+	omitted from PERF output.  May be overridden by the
+	`GIT_TR2_PERF_BRIEF` environment variable.  Defaults to false.
+
+trace2.eventBrief::
+	Boolean.  When true `time`, `filename`, and `line` fields are
+	omitted from event output.  May be overridden by the
+	`GIT_TR2_EVENT_BRIEF` environment variable.  Defaults to false.
+
+trace2.eventNesting::
+	Integer.  Specifies desired depth of nested regions in the
+	event output.  Regions deeper than this value will be
+	omitted.  May be overridden by the `GIT_TR2_EVENT_NESTING`
+	environment variable.  Defaults to 2.
+
+trace2.configParams::
+	A comma-separated list of patterns of "important" config
+	settings that should be recorded in the trace2 output.
+	For example, `core.*,remote.*.url` would cause the trace2
+	output to contain events listing each configured remote.
+	May be overridden by the `GIT_TR2_CONFIG_PARAMS` environment
+	variable.  Unset by default.
+
+trace2.destinationDebug::
+	Boolean.  When true Git will print error messages when a
+	trace target destination cannot be opened for writing.
+	By default, these errors are suppressed and tracing is
+	silently disabled.  May be overridden by the
+	`GIT_TR2_DST_DEBUG` environment variable.
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index 43adbf00eb..8b6a5e6d4b 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -22,21 +22,41 @@ Targets are defined using a VTable allowing easy extension to other
 formats in the future.  This might be used to define a binary format,
 for example.
 
+Trace2 is controlled using `trace2.*` config values in the system and
+global config files and `GIT_TR2*` environment variables.  Trace2 does
+not read from repo local or worktree config files or respect `-c`
+command line config settings.
+
 == Trace2 Targets
 
 Trace2 defines the following set of Trace2 Targets.
 Format details are given in a later section.
 
-`GIT_TR2` (NORMAL)::
+=== The Normal Format Target
+
+The normal format target is a tradition printf format and similar
+to GIT_TRACE format.  This format is enabled with the `GIT_TR`
+environment variable or the `trace2.normalTarget` system or global
+config setting.
+
+For example
 
-	a simple printf format like GIT_TRACE.
-+
 ------------
 $ export GIT_TR2=~/log.normal
 $ git version
 git version 2.20.1.155.g426c96fcdb
 ------------
-+
+
+or
+
+------------
+$ git config --global trace2.normalTarget ~/log.normal
+$ git version
+git version 2.20.1.155.g426c96fcdb
+------------
+
+yields
+
 ------------
 $ cat ~/log.normal
 12:28:42.620009 common-main.c:38                  version 2.20.1.155.g426c96fcdb
@@ -46,17 +66,32 @@ $ cat ~/log.normal
 12:28:42.621250 trace2/tr2_tgt_normal.c:124       atexit elapsed:0.001265 code:0
 ------------
 
-`GIT_TR2_PERF` (PERF)::
+=== The Performance Format Target
+
+The performance format target (PERF) is a column-based format to
+replace GIT_TRACE_PERFORMANCE and is suitable for development and
+testing, possibly to complement tools like gprof.  This format is
+enabled with the `GIT_TR2_PERF` environment variable or the
+`trace2.perfTarget` system or global config setting.
+
+For example
 
-	a column-based format to replace GIT_TRACE_PERFORMANCE suitable for
-	development and testing, possibly to complement tools like gprof.
-+
 ------------
 $ export GIT_TR2_PERF=~/log.perf
 $ git version
 git version 2.20.1.155.g426c96fcdb
 ------------
-+
+
+or
+
+------------
+$ git config --global trace2.perfTarget ~/log.perf
+$ git version
+git version 2.20.1.155.g426c96fcdb
+------------
+
+yields
+
 ------------
 $ cat ~/log.perf
 12:28:42.620675 common-main.c:38                  | d0 | main                     | version      |     |           |           |            | 2.20.1.155.g426c96fcdb
@@ -66,56 +101,46 @@ $ cat ~/log.perf
 12:28:42.621259 trace2/tr2_tgt_perf.c:211         | d0 | main                     | atexit       |     |  0.001265 |           |            | code:0
 ------------
 
-`GIT_TR2_EVENT` (EVENT)::
+=== The Event Format Target
+
+The event format target is a JSON-based format of event data suitable
+for telemetry analysis.  This format is enabled with the `GIT_TR2_EVENT`
+environment variable or the `trace2.eventTarget` system or global config
+setting.
+
+For example
 
-	a JSON-based format of event data suitable for telemetry analysis.
-+
 ------------
 $ export GIT_TR2_EVENT=~/log.event
 $ git version
 git version 2.20.1.155.g426c96fcdb
 ------------
-+
-------------
-$ cat ~/log.event
-{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"}
-{"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]}
-{"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"}
-{"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0}
-{"event":"atexit","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0}
-------------
-
-== Enabling a Target
-
-A Trace2 Target is enabled when the corresponding environment variable
-(`GIT_TR2`, `GIT_TR2_PERF`, or `GIT_TR2_EVENT`) is set.  The following
-values are recognized.
-
-`0`::
-`false`::
-
-	Disables the target.
 
-`1`::
-`true`::
+or
 
-	Enables the target and writes stream to `STDERR`.
-
-`[2-9]`::
+------------
+$ git config --global trace2.eventTarget ~/log.event
+$ git version
+git version 2.20.1.155.g426c96fcdb
+------------
 
-	Enables the target and writes to the already opened file descriptor.
+yields
 
-`<absolute-pathname>`::
+------------
+$ cat ~/log.event
+{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"}
+{"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]}
+{"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"}
+{"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0}
+{"event":"atexit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0}
+------------
 
-	Enables the target, opens and writes to the file in append mode.
+=== Enabling a Target
 
-`af_unix:[<socket_type>:]<absolute-pathname>`::
+To enable a target, set the corresponding environment variable or
+system or global config value to one of the following:
 
-	Enables the target, opens and writes to a Unix Domain Socket
-	(on platforms that support them).
-+
-Socket type can be either `stream` or `dgram`.  If the socket type is
-omitted, Git will try both.
+include::../trace2-target-values.txt[]
 
 == Trace2 API
 
@@ -243,15 +268,16 @@ significantly affects program performance or behavior, such as
 	Emits a "def_param" messages for "important" configuration
 	settings.
 +
-The environment variable `GIT_TR2_CONFIG_PARAMS` can be set to a
+The environment variable `GIT_TR2_CONFIG_PARAMS` or the `trace2.configParams`
+config value can be set to a
 list of patterns of important configuration settings, for example:
 `core.*,remote.*.url`.  This function will iterate over all config
 settings and emit a "def_param" message for each match.
 
 `void trace2_cmd_set_config(const char *key, const char *value)`::
 
-	Emits a "def_param" message for a specific configuration
-	setting IFF it matches the `GIT_TR2_CONFIG_PARAMS` pattern.
+	Emits a "def_param" message for a new or updated key/value
+	pair IF `key` is considered important.
 +
 This is used to hook into `git_config_set()` and catch any
 configuration changes and update a value previously reported by
@@ -418,9 +444,6 @@ recursive tree walk.
 
 === NORMAL Format
 
-NORMAL format is enabled when the `GIT_TR2` environment variable is
-set.
-
 Events are written as lines of the form:
 
 ------------
@@ -437,8 +460,8 @@ Events are written as lines of the form:
 Note that this may contain embedded LF or CRLF characters that are
 not escaped, so the event may spill across multiple lines.
 
-If `GIT_TR2_BRIEF` is true, the `time`, `filename`, and `line` fields
-are omitted.
+If `GIT_TR2_BRIEF` or `trace2.normalBrief` is true, the `time`, `filename`,
+and `line` fields are omitted.
 
 This target is intended to be more of a summary (like GIT_TRACE) and
 less detailed than the other targets.  It ignores thread, region, and
@@ -446,9 +469,6 @@ data messages, for example.
 
 === PERF Format
 
-PERF format is enabled when the `GIT_TR2_PERF` environment variable
-is set.
-
 Events are written as lines of the form:
 
 ------------
@@ -508,8 +528,8 @@ This field is in anticipation of in-proc submodules in the future.
 15:33:33.532712 wt-status.c:2331                  | d0 | main                     | region_leave | r1  |  0.127568 |  0.001504 | status     | label:print
 ------------
 
-If `GIT_TR2_PERF_BRIEF` is true, the `time`, `file`, and `line`
-fields are omitted.
+If `GIT_TR2_PERF_BRIEF` or `trace2.perfBrief` is true, the `time`, `file`,
+and `line` fields are omitted.
 
 ------------
 d0 | main                     | region_leave | r1  |  0.011717 |  0.009122 | index      | label:preload
@@ -520,9 +540,6 @@ during development and is quite noisy.
 
 === EVENT Format
 
-EVENT format is enabled when the `GIT_TR2_EVENT` environment
-variable is set.
-
 Each event is a JSON-object containing multiple key/value pairs
 written as a single line and followed by a LF.
 
@@ -540,7 +557,7 @@ The following key/value pairs are common to all events:
 ------------
 {
 	"event":"version",
-	"sid":"20190408T191827.272759Z-H9b68c35f-P011764",
+	"sid":"20190408T191827.272759Z-H9b68c35f-P00003510",
 	"thread":"main",
 	"time":"2019-04-08T19:18:27.282761Z",
 	"file":"common-main.c",
@@ -576,9 +593,9 @@ The following key/value pairs are common to all events:
 `"repo":<repo-id>`::
 	when present, is the integer repo-id as described previously.
 
-If `GIT_TR2_EVENT_BRIEF` is true, the `file` and `line` fields are omitted
-from all events and the `time` field is only present on the "start" and
-"atexit" events.
+If `GIT_TR2_EVENT_BRIEF` or `trace2.eventBrief` is true, the `file`
+and `line` fields are omitted from all events and the `time` field is
+only present on the "start" and "atexit" events.
 
 ==== Event-Specific Key/Value Pairs
 
@@ -889,7 +906,7 @@ visited.
 The `category` field may be used in a future enhancement to
 do category-based filtering.
 +
-The `GIT_TR2_EVENT_NESTING` environment variable can be used to
+`GIT_TR2_EVENT_NESTING` or `trace2.eventNesting` can be used to
 filter deeply nested regions and data events.  It defaults to "2".
 
 `"region_leave"`::
diff --git a/Documentation/trace2-target-values.txt b/Documentation/trace2-target-values.txt
new file mode 100644
index 0000000000..27d3c64e66
--- /dev/null
+++ b/Documentation/trace2-target-values.txt
@@ -0,0 +1,10 @@
+--
+* `0` or `false` - Disables the target.
+* `1` or `true` - Writes to `STDERR`.
+* `[2-9]` - Writes to the already opened file descriptor.
+* `<absolute-pathname>` - Writes to the file in append mode.
+* `af_unix:[<socket_type>:]<absolute-pathname>` - Write to a
+Unix DomainSocket (on platforms that support them).  Socket
+type can be either `stream` or `dgram`; if omitted Git will
+try both.
+--