The layer of shims here seems a bit wasteful compared to just calling
the corresponding string map functions directly, but it allows control
over the API (calling with notmuch_database_t *) and flexibility for
future changes.
---
 lib/config.cc          | 39 ++++++++++++++++++++++++++++++
 lib/notmuch.h          | 21 ++++++++++++++++
 test/T590-libconfig.sh | 54 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+)

diff --git a/lib/config.cc b/lib/config.cc
index cec2e9de..de919b87 100644
--- a/lib/config.cc
+++ b/lib/config.cc
@@ -38,6 +38,10 @@ struct _notmuch_config_values {
     void *children; /* talloc_context */
 };
 
+struct _notmuch_config_pairs {
+    notmuch_string_map_iterator_t *iter;
+};
+
 static const char * _notmuch_config_key_to_string (notmuch_config_key_t key);
 
 static int
@@ -331,6 +335,41 @@ notmuch_config_values_destroy (notmuch_config_values_t *values) {
     talloc_free (values);
 }
 
+notmuch_config_pairs_t *
+notmuch_config_get_pairs (notmuch_database_t *notmuch,
+			  const char *prefix)
+{
+    notmuch_config_pairs_t *pairs = talloc(notmuch,notmuch_config_pairs_t);
+    pairs->iter = _notmuch_string_map_iterator_create (notmuch->config, prefix, false);
+    return pairs;
+}
+
+notmuch_bool_t
+notmuch_config_pairs_valid (notmuch_config_pairs_t *pairs) {
+    return _notmuch_string_map_iterator_valid (pairs->iter);
+}
+
+void
+notmuch_config_pairs_move_to_next (notmuch_config_pairs_t *pairs) {
+    _notmuch_string_map_iterator_move_to_next (pairs->iter);
+}
+
+const char *
+notmuch_config_pairs_key (notmuch_config_pairs_t *pairs) {
+    return _notmuch_string_map_iterator_key (pairs->iter);
+}
+
+const char *
+notmuch_config_pairs_value (notmuch_config_pairs_t *pairs) {
+    return _notmuch_string_map_iterator_value (pairs->iter);
+}
+
+void
+notmuch_config_pairs_destroy (notmuch_config_pairs_t *pairs) {
+    _notmuch_string_map_iterator_destroy (pairs->iter);
+    talloc_free (pairs);
+}
+
 notmuch_status_t
 _notmuch_config_load_from_file (notmuch_database_t *notmuch,
 				GKeyFile *file)
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 9a4f94f5..f050d2b6 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -245,6 +245,7 @@ typedef struct _notmuch_directory notmuch_directory_t;
 typedef struct _notmuch_filenames notmuch_filenames_t;
 typedef struct _notmuch_config_list notmuch_config_list_t;
 typedef struct _notmuch_config_values notmuch_config_values_t;
+typedef struct _notmuch_config_pairs notmuch_config_pairs_t;
 typedef struct _notmuch_indexopts notmuch_indexopts_t;
 #endif /* __DOXYGEN__ */
 
@@ -2638,6 +2639,26 @@ notmuch_config_values_start (notmuch_config_values_t *values);
 void
 notmuch_config_values_destroy (notmuch_config_values_t *values);
 
+
+notmuch_config_pairs_t *
+notmuch_config_get_pairs (notmuch_database_t *notmuch,
+			  const char *prefix);
+
+notmuch_bool_t
+notmuch_config_pairs_valid (notmuch_config_pairs_t *pairs);
+
+void
+notmuch_config_pairs_move_to_next (notmuch_config_pairs_t *pairs);
+
+const char *
+notmuch_config_pairs_key (notmuch_config_pairs_t *pairs);
+
+const char *
+notmuch_config_pairs_value (notmuch_config_pairs_t *pairs);
+
+void
+notmuch_config_pairs_destroy (notmuch_config_pairs_t *pairs);
+
 /**
  * get a configuration value from an open database as Boolean
  *
diff --git a/test/T590-libconfig.sh b/test/T590-libconfig.sh
index edbba6c4..49cc382a 100755
--- a/test/T590-libconfig.sh
+++ b/test/T590-libconfig.sh
@@ -770,5 +770,59 @@ EOF
 test_expect_equal_file EXPECTED OUTPUT
 restore_database
 
+test_begin_subtest "notmuch_config_get_pairs: prefix (ndlc)"
+cat c_head2 - c_tail <<'EOF' | test_C ${MAIL_DIR} ${NOTMUCH_CONFIG} %NULL%
+{
+   notmuch_config_pairs_t *list;
+   for (list =  notmuch_config_get_pairs (db, "user.");
+        notmuch_config_pairs_valid (list);
+        notmuch_config_pairs_move_to_next (list)) {
+     printf("%s %s\n", notmuch_config_pairs_key (list), notmuch_config_pairs_value(list));
+   }
+   notmuch_config_pairs_destroy (list);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+user.name Notmuch Test Suite
+user.other_email test_suite_other@notmuchmail.org;test_suite@otherdomain.org
+user.primary_email test_suite@notmuchmail.org
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "notmuch_config_get_pairs: all pairs (ndlc)"
+cat c_head2 - c_tail <<'EOF' | test_C ${MAIL_DIR} ${NOTMUCH_CONFIG} %NULL%
+{
+   notmuch_config_pairs_t *list;
+   for (list =  notmuch_config_get_pairs (db, "");
+        notmuch_config_pairs_valid (list);
+        notmuch_config_pairs_move_to_next (list)) {
+     printf("%s %s\n", notmuch_config_pairs_key (list), notmuch_config_pairs_value(list));
+   }
+   notmuch_config_pairs_destroy (list);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+aaabefore beforeval
+database.backup_dir MAIL_DIR/.notmuch/backups
+database.hook_dir MAIL_DIR/.notmuch/hooks
+database.mail_root MAIL_DIR
+database.path MAIL_DIR
+key with spaces value, with, spaces!
+maildir.synchronize_flags true
+new.ignore sekrit_junk
+new.tags unread;inbox;
+search.exclude_tags foo;bar;fub
+test.key1 testvalue1
+test.key2 testvalue2
+user.name Notmuch Test Suite
+user.other_email test_suite_other@notmuchmail.org;test_suite@otherdomain.org
+user.primary_email test_suite@notmuchmail.org
+zzzafter afterval
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
 
 test_done
-- 
2.30.1
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