trace2: teach Git to log environment variables

Via trace2, Git can already log interesting config parameters (see the
trace2_cmd_list_config() function). However, this can grant an
incomplete picture because many config parameters also allow overrides
via environment variables.

To allow for more complete logs, we add a new trace2_cmd_list_env_vars()
function and supporting implementation, modeled after the pre-existing
config param logging implementation.

Signed-off-by: Josh Steadmon <steadmon@google.com>
Acked-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/trace2/tr2_cfg.c b/trace2/tr2_cfg.c
index caa7f06..ec9ac1a 100644
--- a/trace2/tr2_cfg.c
+++ b/trace2/tr2_cfg.c
@@ -7,6 +7,10 @@ static struct strbuf **tr2_cfg_patterns;
 static int tr2_cfg_count_patterns;
 static int tr2_cfg_loaded;
 
+static struct strbuf **tr2_cfg_env_vars;
+static int tr2_cfg_env_vars_count;
+static int tr2_cfg_env_vars_loaded;
+
 /*
  * Parse a string containing a comma-delimited list of config keys
  * or wildcard patterns into a list of strbufs.
@@ -46,6 +50,45 @@ void tr2_cfg_free_patterns(void)
 	tr2_cfg_loaded = 0;
 }
 
+/*
+ * Parse a string containing a comma-delimited list of environment variable
+ * names into a list of strbufs.
+ */
+static int tr2_load_env_vars(void)
+{
+	struct strbuf **s;
+	const char *varlist;
+
+	if (tr2_cfg_env_vars_loaded)
+		return tr2_cfg_env_vars_count;
+	tr2_cfg_env_vars_loaded = 1;
+
+	varlist = tr2_sysenv_get(TR2_SYSENV_ENV_VARS);
+	if (!varlist || !*varlist)
+		return tr2_cfg_env_vars_count;
+
+	tr2_cfg_env_vars = strbuf_split_buf(varlist, strlen(varlist), ',', -1);
+	for (s = tr2_cfg_env_vars; *s; s++) {
+		struct strbuf *buf = *s;
+
+		if (buf->len && buf->buf[buf->len - 1] == ',')
+			strbuf_setlen(buf, buf->len - 1);
+		strbuf_trim_trailing_newline(*s);
+		strbuf_trim(*s);
+	}
+
+	tr2_cfg_env_vars_count = s - tr2_cfg_env_vars;
+	return tr2_cfg_env_vars_count;
+}
+
+void tr2_cfg_free_env_vars(void)
+{
+	if (tr2_cfg_env_vars)
+		strbuf_list_free(tr2_cfg_env_vars);
+	tr2_cfg_env_vars_count = 0;
+	tr2_cfg_env_vars_loaded = 0;
+}
+
 struct tr2_cfg_data {
 	const char *file;
 	int line;
@@ -79,6 +122,21 @@ void tr2_cfg_list_config_fl(const char *file, int line)
 		read_early_config(tr2_cfg_cb, &data);
 }
 
+void tr2_list_env_vars_fl(const char *file, int line)
+{
+	struct strbuf **s;
+
+	if (tr2_load_env_vars() <= 0)
+		return;
+
+	for (s = tr2_cfg_env_vars; *s; s++) {
+		struct strbuf *buf = *s;
+		const char *val = getenv(buf->buf);
+		if (val && *val)
+			trace2_def_param_fl(file, line, buf->buf, val);
+	}
+}
+
 void tr2_cfg_set_fl(const char *file, int line, const char *key,
 		    const char *value)
 {