Add --log-append option

Add --log-append option which makes tio append to any existing log file.

This also changes the default behaviour of tio from appending to
overwriting any existing log file. Now you have to use this new option
to make tio append.

src/configfile.c

@@ -198,6 +198,10 @@ static int data_handler(void *user, const char *section, const char *name,
             asprintf(&c.log_filename, "%s", value);
             option.log_filename = c.log_filename;
         }
+        else if (!strcmp(name, "log-append"))
+        {
+            option.log_append = read_boolean(value, name);
+        }
         else if (!strcmp(name, "log-strip"))
         {
             option.log_strip = read_boolean(value, name);

src/log.c

@@ -69,8 +69,17 @@ int log_open(const char *filename)
 
     log_filename = filename;
 
-    // Open log file in append write mode
-    fp = fopen(filename, "a+");
+    // Open log file
+    if (option.log_append)
+    {
+        // Appends to existing log file
+        fp = fopen(filename, "a+");
+    }
+    else
+    {
+        // Truncates existing log file
+        fp = fopen(filename, "w+");
+    }
     if (fp == NULL)
     {
         tio_warning_printf("Could not open log file %s (%s)", filename, strerror(errno));

src/options.c

@@ -74,6 +74,7 @@ struct option_t option =
     .ri_pulse_duration = 100,
     .no_autoconnect = false,
     .log = false,
+    .log_append = false,
     .log_filename = NULL,
     .log_strip = false,
     .local_echo = false,
@@ -119,6 +120,7 @@ void print_help(char *argv[])
     printf("  -L, --list-devices                     List available serial devices by ID\n");
     printf("  -l, --log                              Enable log to file\n");
     printf("      --log-file <filename>              Set log filename\n");
+    printf("      --log-append                       Append to log file\n");
     printf("      --log-strip                        Strip control characters and escape sequences\n");
     printf("  -m, --map <flags>                      Map characters\n");
     printf("  -c, --color 0..255|bold|none|list      Colorize tio text (default: bold)\n");

src/options.h

@@ -48,6 +48,7 @@ struct option_t
     unsigned int ri_pulse_duration;
     bool no_autoconnect;
     bool log;
+    bool log_append;
     bool log_strip;
     bool local_echo;
     enum timestamp_t timestamp;