[PATCH 0/4] trace2: move 'def_param' events into 'cmd_name' and 'cmd_alias'

Some Git commands do not emit def_param events for interesting config and environment variable settings. Let's fix that.

Builtin commands compiled into git.c have the normal control flow and emit a cmd_name event and then def_param events for each interesting config and environment variable. However, some special "query" commands, like --exec-path, or some forms of alias expansion, emitted a cmd_name but did not emit def_param events.

Also, special commands git-remote-https is built from remote-curl.c and git-http-fetch is built from http-fetch.c and do not use the normal set up in git.c. These emitted a cmd_name but not def_param events.

To minimize the footprint of this commit, move the calls to trace2_cmd_list_config() and trace2_cmd_list_env_vars() into trace2_cmd_name() and trace2_cmd_alias() so that we always get a set def_param events when a cmd_name or cmd_alias event is generated.

Users can define local config settings on a repo to classify/name a repo (e.g. "project-foo" vs "personal") and use the def_param feature to label Trace2 data so that (a third-party) telemetry service does not collect data on personal repos or so that telemetry from one work repo is distinguishable from another work repo.

Jeff Hostetler (4):
  t0211: demonstrate missing 'def_param' events for certain commands
  trace2: avoid emitting 'def_param' set more than once
  trace2: emit 'def_param' set with 'cmd_name' event
  trace2: remove unneeded calls to generate 'def_param' set

 git.c                  |   6 --
 t/t0211-trace2-perf.sh | 231 +++++++++++++++++++++++++++++++++++++++++
 trace2.c               |  15 +++
 3 files changed, 246 insertions(+), 6 deletions(-)

base-commit: 0f9d4d28b7e6021b7e6db192b7bf47bd3a0d0d1d
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1679%2Fjeffhostetler%2Falways-emit-def-param-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1679/jeffhostetler/always-emit-def-param-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1679