The watchgit works but I don't think I really need libgit2 at all if I can just process the .gitignore correctly.

.gitignore

@@ -10,3 +10,4 @@ builddir
 subprojects
 *.csv
 *.exe
+*.dll

regtest.cpp

@@ -7,12 +7,13 @@ using namespace std;
 
 int main(int argc, char *argv[]) {
   smatch matches;
-  regex to_test(argv[1]);
-  string line(argv[2]);
 
   if(argc != 3) {
     println("USAGE: regtest <regex> <line>");
   } else {
+    regex to_test(argv[1]);
+    string line(argv[2]);
+
     if(regex_match(line, matches, to_test)) {
       println("MATCHED: ");
 

watchgit.cpp

@@ -2,6 +2,7 @@
 #include <iomanip>
 #include <fstream>
 #include <fmt/core.h>
+#include <fmt/chrono.h>
 #include <regex>
 #include <string>
 #include <iterator>
@@ -114,8 +115,7 @@ void run_build(const char* command) {
   char buffer[BUF_MAX]; // BUF_MAX is a define already?
   ofstream stats_out;
   stats_out.open("stats.csv", ios::out | ios::app);
-  auto t = time(nullptr);
-  auto tm = *std::gmtime(&t);
+  std::time_t tstamp = std::time(nullptr);
 
   dbc::check(stats_out.good(), "Error opening stats.csv file.");
   dbc::pre("simple test", [&]() { return stats_out.good(); });
@@ -136,13 +136,12 @@ void run_build(const char* command) {
       string type = err[4].str();
       string message = err[5].str();
 
-      stats_out << put_time(&tm, "%FT%TZ");
-      string result = format(",{},{},{},{},{}\n", file_name, lnumber, col, type, message);
+      string result = format("{:%FT%T},{},{},{},{},{}\n",
+          fmt::localtime(tstamp), file_name,
+          lnumber, col, type, message);
 
       stats_out << result;
       cout << "MATCHED: " << quoted(result);
-    } else {
-      //println("NOT MATCHED! {}", line);
     }
   }