Subject: [PATCH v3 3/4] trace.c: print env vars in trace_run_command()

From: Nguyễn Thái Ngọc Duy <[email-masked]>
Date: Fri, 12 Jan 2018 16:56:06 +0700

Occasionally submodule code could execute new commands with GIT_DIR set
to some submodule. GIT_TRACE prints just the command line which makes it
hard to tell that it's not really executed on this repository.

Print modified env variables (compared to parent environment) in this
case. Actually only modified or new variables (*) are printed. Variable
deletion is suppressed because they are often used to clean up
repo-specific variables that git passes around between processes. When
submodule code executes commands on another repo, it clears all these
variables, _many_ of these, that make the output really noisy.

(*) sort of. More on this in the next patch.

Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
---
 trace.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/trace.c b/trace.c
index ed1f728021..e499074d39 100644
--- a/trace.c
+++ b/trace.c
@@ -273,6 +273,24 @@ void trace_performance_fl(const char *file, int line, uint64_t nanos,
 #endif /* HAVE_VARIADIC_MACROS */

+static void concatenate_env(struct strbuf *dst, const char *const *envs)
+{
+	int i;
+
+	for (i = 0; envs[i]; i++) {
+		const char *env = envs[i];
+		const char *p = strchr(env, '=');
+
+		if (!p) /* ignore var deletion for now */
+			continue;
+		p++;
+
+		strbuf_addch(dst, ' ');
+		strbuf_add(dst, env, p - env);
+		sq_quote_buf(dst, p);
+	}
+}
+
 void trace_run_command(const struct child_process *cp)
 {
 	struct strbuf buf = STRBUF_INIT;
@@ -281,8 +299,17 @@ void trace_run_command(const struct child_process *cp)
 				&trace_default_key, &buf))
 		return;
 
+	strbuf_grow(&buf, 255);
+
 	strbuf_addf(&buf, "trace: run_command:");
 
+	/*
+	 * The caller is responsible for initializing cp->env from
+	 * cp->env_array if needed. We only check one place.
+	 */
+	if (cp->env)
+		concatenate_env(&buf, cp->env);
+
 	if (cp->git_cmd)
 		strbuf_addstr(&buf, " git");
 
-- 
2.15.1.600.g899a5f85c6