mingw: really handle SIGINT

Previously, we did not install any handler for Ctrl+C, but now we really
want to because the MSYS2 runtime learned the trick to call the
ConsoleCtrlHandler when Ctrl+C was pressed.

With this, hitting Ctrl+C while `git log` is running will only terminate
the Git process, but not the pager. This finally matches the behavior on
Linux and on macOS.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

compat/mingw.c

@@ -3772,7 +3772,14 @@ static void adjust_symlink_flags(void)
 		symlink_file_flags |= 2;
 		symlink_directory_flags |= 2;
 	}
+}
 
+static BOOL WINAPI handle_ctrl_c(DWORD ctrl_type)
+{
+	if (ctrl_type != CTRL_C_EVENT)
+		return FALSE; /* we did not handle this */
+	mingw_raise(SIGINT);
+	return TRUE; /* we did handle this */
 }
 
 #ifdef _MSC_VER
@@ -3808,6 +3815,8 @@ int wmain(int argc, const wchar_t **wargv)
 #endif
 #endif
 
+	SetConsoleCtrlHandler(handle_ctrl_c, TRUE);
+
 	maybe_redirect_std_handles();
 	adjust_symlink_flags();
 	fsync_object_files = 1;