cli: add --batch option to notmuch count

Add support for reading queries from stdin, one per line, and writing
results to stdout, one per line.

This will bring considerable performance improvements when utilized in
Emacs notmuch-hello, especially so when running remote notmuch.

notmuch-count.c

@@ -62,6 +62,27 @@ print_count (notmuch_database_t *notmuch, const char *query_str,
     return 0;
 }
 
+static int
+count_file (notmuch_database_t *notmuch, FILE *input, const char **exclude_tags,
+	    size_t exclude_tags_length, int output)
+{
+    char *line = NULL;
+    ssize_t line_len;
+    size_t line_size;
+    int ret = 0;
+
+    while (!ret && (line_len = getline (&line, &line_size, input)) != -1) {
+	chomp_newline (line);
+	ret = print_count (notmuch, line, exclude_tags, exclude_tags_length,
+			   output);
+    }
+
+    if (line)
+	free (line);
+
+    return ret;
+}
+
 int
 notmuch_count_command (notmuch_config_t *config, int argc, char *argv[])
 {
@@ -72,6 +93,9 @@ notmuch_count_command (notmuch_config_t *config, int argc, char *argv[])
     int exclude = EXCLUDE_TRUE;
     const char **search_exclude_tags = NULL;
     size_t search_exclude_tags_length = 0;
+    notmuch_bool_t batch = FALSE;
+    FILE *input = stdin;
+    char *input_file_name = NULL;
     int ret;
 
     notmuch_opt_desc_t options[] = {
@@ -83,6 +107,8 @@ notmuch_count_command (notmuch_config_t *config, int argc, char *argv[])
 	  (notmuch_keyword_t []){ { "true", EXCLUDE_TRUE },
 				  { "false", EXCLUDE_FALSE },
 				  { 0, 0 } } },
+	{ NOTMUCH_OPT_BOOLEAN, &batch, "batch", 0, 0 },
+	{ NOTMUCH_OPT_STRING, &input_file_name, "input", 'i', 0 },
 	{ 0, 0, 0, 0, 0 }
     };
 
@@ -92,6 +118,21 @@ notmuch_count_command (notmuch_config_t *config, int argc, char *argv[])
 	return 1;
     }
 
+    if (input_file_name) {
+	batch = TRUE;
+	input = fopen (input_file_name, "r");
+	if (input == NULL) {
+	    fprintf (stderr, "Error opening %s for reading: %s\n",
+		     input_file_name, strerror (errno));
+	    return 1;
+	}
+    }
+
+    if (batch && opt_index != argc) {
+	fprintf (stderr, "--batch and query string are not compatible\n");
+	return 1;
+    }
+
     if (notmuch_database_open (notmuch_config_get_database_path (config),
 			       NOTMUCH_DATABASE_MODE_READ_ONLY, &notmuch))
 	return 1;
@@ -107,10 +148,17 @@ notmuch_count_command (notmuch_config_t *config, int argc, char *argv[])
 	    (config, &search_exclude_tags_length);
     }
 
-    ret = print_count (notmuch, query_str, search_exclude_tags,
+    if (batch)
-		       search_exclude_tags_length, output);
+	ret = count_file (notmuch, input, search_exclude_tags,
+			  search_exclude_tags_length, output);
+    else
+	ret = print_count (notmuch, query_str, search_exclude_tags,
+			   search_exclude_tags_length, output);
 
     notmuch_database_destroy (notmuch);
 
+    if (input != stdin)
+	fclose (input);
+
     return ret;
 }