notmuch: Add a new "notmuch config" command for querying configuration.

So far, we implement only "notmuch config get". It won't be too much
work from here to also implement "notmuch config set".

notmuch-client.h

@@ -113,6 +113,9 @@ notmuch_search_tags_command (void *ctx, int argc, char *argv[]);
 int
 notmuch_part_command (void *ctx, int argc, char *argv[]);
 
+int
+notmuch_config_command (void *ctx, int argc, char *argv[]);
+
 const char *
 notmuch_time_relative_date (const void *ctx, time_t then);
 
@@ -174,7 +177,7 @@ void
 notmuch_config_set_user_primary_email (notmuch_config_t *config,
 				       const char *primary_email);
 
-char **
+const char **
 notmuch_config_get_user_other_email (notmuch_config_t *config,
 				     size_t *length);
 

notmuch-config.c

@@ -68,7 +68,7 @@ struct _notmuch_config {
     char *database_path;
     char *user_name;
     char *user_primary_email;
-    char **user_other_email;
+    const char **user_other_email;
     size_t user_other_email_length;
     const char **new_tags;
     size_t new_tags_length;
@@ -474,7 +474,7 @@ notmuch_config_set_user_primary_email (notmuch_config_t *config,
     config->user_primary_email = NULL;
 }
 
-char **
+const char **
 notmuch_config_get_user_other_email (notmuch_config_t *config,
 				     size_t *length)
 {
@@ -562,3 +562,56 @@ notmuch_config_set_new_tags (notmuch_config_t *config,
     config->new_tags = NULL;
 }
 
+int
+notmuch_config_command (void *ctx, int argc, char *argv[])
+{
+    notmuch_config_t *config;
+    const char *item;
+
+    if (argc != 2) {
+	fprintf (stderr, "Error: notmuch config requires two arguments.\n");
+	return 1;
+    }
+
+    if (strcmp (argv[0], "get")) {
+	fprintf (stderr, "Unrecognized argument for notmuch config: %s\n",
+		 argv[0]);
+	return 1;
+    }
+
+    config = notmuch_config_open (ctx, NULL, NULL);
+    if (config == NULL)
+	return 1;
+
+    item = argv[1];
+
+    if (strcmp(item, "database.path") == 0) {
+	printf ("%s\n", notmuch_config_get_database_path (config));
+    } else if (strcmp(item, "user.name") == 0) {
+	printf ("%s\n", notmuch_config_get_user_name (config));
+    } else if (strcmp(item, "user.primary_email") == 0) {
+	printf ("%s\n", notmuch_config_get_user_primary_email (config));
+    } else if (strcmp(item, "user.other_email") == 0) {
+	const char **other_email;
+	size_t i, length;
+	
+	other_email = notmuch_config_get_user_other_email (config, &length);
+	for (i = 0; i < length; i++)
+	    printf ("%s\n", other_email[i]);
+    } else if (strcmp(item, "new.tags") == 0) {
+	const char **tags;
+	size_t i, length;
+
+	tags = notmuch_config_get_new_tags (config, &length);
+	for (i = 0; i < length; i++)
+	    printf ("%s\n", tags[i]);
+    } else {
+	fprintf (stderr, "Unknown configuration item: %s\n",
+		 argv[1]);
+	return 1;
+    }
+
+    notmuch_config_close (config);
+
+    return 0;
+}

notmuch.1

@@ -404,6 +404,34 @@ See the
 section below for details of the supported syntax for <search-terms>.
 .RE
 
+The
+.B config
+command can be used to get settings from the notmuch configuration
+file.
+
+.RS 4
+.TP 4
+.BR "config get " <section> . <item>
+
+Get settings from the notmuch configuration file.
+
+The value of the specified configuration item is printed to stdout. If
+the item has multiple values, each value is separated by a newline
+character.
+
+Available configuration items include at least
+
+	database.path
+
+	user.name
+
+	user.primary_email
+
+	user.other_email
+
+	new.tags
+.RE
+
 .SH SEARCH SYNTAX
 Several notmuch commands accept a common syntax for search terms.
 

notmuch.c

@@ -321,6 +321,20 @@ command_t commands[] = {
       "\tby the \"--format=json\" option of \"notmuch show\". If the\n"
       "\tmessage specified by the search terms does not include a\n"
       "\tpart with the specified \"id\" there will be no output." },
+    { "config", notmuch_config_command,
+      "get <section>.<item>",
+      "Get settings from the notmuch configuration file.",
+      "\tThe value of the specified configuration item is printed\n"
+      "\tto stdout. If the item has multiple values, each value\n"
+      "\tis separated by a newline character.\n"
+      "\n"
+      "\tAvailable configuration items include at least"
+      "\n"
+      "\t\tdatabase.path\n"
+      "\t\tuser.name\n"
+      "\t\tuser.primary_email\n"
+      "\t\tuser.other_email\n"
+      "\t\tnew.tags\n" },
     { "help", notmuch_help_command,
       "[<command>]",
       "This message, or more detailed help for the named command.",