+
+static char **prep_childenv(const char *const *deltaenv)
+{
+ extern char **environ;
+ char **childenv;
+ struct string_list env = STRING_LIST_INIT_DUP;
+ struct strbuf key = STRBUF_INIT;
+ const char *const *p;
+ int i;
+
+ /* Construct a sorted string list consisting of the current environ */
+ for (p = (const char *const *) environ; p && *p; p++) {
+ const char *equals = strchr(*p, '=');
+
+ if (equals) {
+ strbuf_reset(&key);
+ strbuf_add(&key, *p, equals - *p);
+ string_list_append(&env, key.buf)->util = (void *) *p;
+ } else {
+ string_list_append(&env, *p)->util = (void *) *p;
+ }
+ }
+ string_list_sort(&env);
+
+ /* Merge in 'deltaenv' with the current environ */
+ for (p = deltaenv; p && *p; p++) {
+ const char *equals = strchr(*p, '=');
+
+ if (equals) {
+ /* ('key=value'), insert or replace entry */
+ strbuf_reset(&key);
+ strbuf_add(&key, *p, equals - *p);
+ string_list_insert(&env, key.buf)->util = (void *) *p;
+ } else {
+ /* otherwise ('key') remove existing entry */
+ string_list_remove(&env, *p, 0);
+ }
+ }
+
+ /* Create an array of 'char *' to be used as the childenv */
+ childenv = xmalloc((env.nr + 1) * sizeof(char *));
+ for (i = 0; i < env.nr; i++)
+ childenv[i] = env.items[i].util;
+ childenv[env.nr] = NULL;
+
+ string_list_clear(&env, 0);
+ strbuf_release(&key);
+ return childenv;
+}