Report regex engine in libgit2_config()

Author: iofarm

src/utils.h

@@ -23,7 +23,7 @@ git_strarray *files_to_array(SEXP files);
 
 #define build_tibble(...) list_to_tibble(build_list( __VA_ARGS__))
 
-#define AT_LEAST_LIBGIT2(x,y) (LIBGIT2_VER_MAJOR > x || LIBGIT2_VER_MINOR >= y)
+#define AT_LEAST_LIBGIT2(x,y) (LIBGIT2_VER_MAJOR > x || (LIBGIT2_VER_MAJOR >= x && LIBGIT2_VER_MINOR >= y))
 
 /* Workaround for API change in 1.8.0 and 1.8.1 only: https://github.com/libgit2/libgit2/issues/6793 */
 #if LIBGIT2_VER_MAJOR == 1 && LIBGIT2_VER_MINOR == 8 && LIBGIT2_VER_REVISION < 2

src/version.c

@@ -25,6 +25,13 @@ SEXP R_libgit2_config(void){
   SEXP ssh = PROTECT(Rf_ScalarLogical(features & GIT_FEATURE_SSH));
   SEXP https = PROTECT(Rf_ScalarLogical(features & GIT_FEATURE_HTTPS));
   SEXP threads = PROTECT(Rf_ScalarLogical(features & GIT_FEATURE_THREADS));
+  const char* c_regex_backend;
+#if AT_LEAST_LIBGIT2(1, 9)
+  c_regex_backend = git_libgit2_feature_backend(GIT_FEATURE_REGEX);
+#else
+  c_regex_backend = "unknown";
+#endif
+  SEXP regex_backend = PROTECT(safe_string(c_regex_backend));
   git_buf buf = {0};
   git_config_find_global(&buf);
   SEXP config_global = PROTECT(safe_string(buf.ptr));
@@ -35,9 +42,10 @@ SEXP R_libgit2_config(void){
   git_libgit2_opts(GIT_OPT_GET_SEARCH_PATH, GIT_CONFIG_LEVEL_GLOBAL, &buf);
   SEXP config_search_path = PROTECT(safe_string(buf.ptr));
   git_buf_free(&buf);
-  SEXP out = build_list(7, "version", version, "ssh", ssh, "https", https, "threads", threads,
+  SEXP out = build_list(8, "version", version, "ssh", ssh, "https", https, "threads", threads,
+                    "regex_backend", regex_backend,
                     "config.global", config_global, "config.system", config_system,
                     "config.home", config_search_path);
-  UNPROTECT(7);
+  UNPROTECT(8);
   return out;
 }