Not only Git has a GIT_TRACE2 flag (since Git 2.25, Q2 2019), but now that trace can even tell you what parent process called Git.
With Git 2.34 (Q4 2021), trace2 logs learned to show parent process name to see in what context Git was invoked.
That is helpful when Git is called by an IDE.
See commit 2f732bf, commit b7e6a41 (21 Jul 2021) by Emily Shaffer (nasamuffin
).
(Merged by Junio C Hamano -- gitster
-- in commit 6f64eea, 24 Aug 2021)
tr2
: log parent process name
Signed-off-by: Emily Shaffer
It can be useful to tell who invoked Git - was it invoked manually by a user via CLI or script? By an IDE? In some cases - like 'repo' tool - we can influence the source code and set the GIT_TRACE2_PARENT_SID
environment variable from the caller process.
In 'repo''s case, that parent SID is manipulated to include the string "repo", which means we can positively identify when Git was invoked by 'repo' tool.
However, identifying parents that way requires both that we know which tools invoke Git and that we have the ability to modify the source code of those tools.
It cannot scale to keep up with the various IDEs and wrappers which use Git, most of which we don't know about.
Learning which tools and wrappers invoke Git, and how, would give us insight to decide where to improve Git's usability and performance.
Unfortunately, there's no cross-platform reliable way to gather the name of the parent process.
If procfs
is present, we can use that; otherwise we will need to discover the name another way.
However, the process ID should be sufficient to look up the process name on most platforms, so that code may be shareable.
Git for Windows gathers similar information and logs it as a "data_json"
event.
However, since "data_json"
has a variable format, it is difficult to parse effectively in some languages; instead, let's pursue a dedicated "cmd_ancestry"
event to record information about the ancestry of the current process and a consistent, parseable way.
Git for Windows also gathers information about more than one generation of parent.
In Linux further ancestry info can be gathered with procfs
, but it's unwieldy to do so.
In the interest of later moving Git for Windows ancestry logging to the 'cmd_ancestry
' event, and in the interest of later adding more ancestry to the Linux implementation - or of adding this functionality to other platforms which have an easier time walking the process tree - let's make 'cmd_ancestry
' accept an array of parentage.
technical/api-trace2
now includes in its man page:
"cmd_ancestry"
This event contains the text command name for the parent (and earlier
generations of parents) of the current process, in an array ordered from
nearest parent to furthest great-grandparent. It may not be implemented
on all platforms.
------------
{
"event":"cmd_ancestry",
...
"ancestry":["bash","tmux: server","systemd"]
}
------------
With Git 2.34 (Q4 2021), the tracing of process ancestry information has been enhanced.
See commit 2d3491b, commit 326460a, commit 6eccfc3, commit 48f6871, commit f2cc888, commit 7d9c80f (27 Aug 2021) by Ævar Arnfjörð Bjarmason (avar
).
(Merged by Junio C Hamano -- gitster
-- in commit 76f5fdc, 20 Sep 2021)
tr2
: tr2
: log N
parent process names on Linux
Signed-off-by: Ævar Arnfjörð Bjarmason
Acked-by: Taylor Blau
In 2f732bf ("tr2
: log parent process name", 2021-07-21, Git v2.34.0 -- merge we started
logging parent process names, but only logged all parents on Windows.
on Linux only the name of the immediate parent process was logged.
Extend the functionality added there to also log full parent chain on
Linux.