cli: add support for pre and post notmuch new hooks

Run notmuch new pre and post hooks, named "pre-new" and "post-new", if
present in the notmuch hooks directory. The hooks will be run before and
after incorporating new messages to the database.

Typical use cases for pre-new and post-new hooks are fetching or delivering
new mail to the maildir, and custom tagging of the mail incorporated to the
database.

Also add command line option --no-hooks to notmuch new to bypass the hooks.

Signed-off-by: Jani Nikula <jani@nikula.org>

NEWS

@@ -1,6 +1,16 @@
 Notmuch 0.11 (201x-xx-xx)
 =========================
 
+New command-line features
+-------------------------
+
+Hooks
+
+  Hooks have been introduced to notmuch. Hooks are scripts that notmuch
+  invokes before and after certain actions. Initially, "notmuch new"
+  supports "pre-new" and "post-new" hooks that are run before and after
+  importing new messages into the database.
+
 Performance
 -----------
 

notmuch-new.c

@@ -811,6 +811,7 @@ notmuch_new_command (void *ctx, int argc, char *argv[])
     _filename_node_t *f;
     int i;
     notmuch_bool_t timer_is_active = FALSE;
+    notmuch_bool_t run_hooks = TRUE;
 
     add_files_state.verbose = 0;
     add_files_state.output_is_a_tty = isatty (fileno (stdout));
@@ -820,6 +821,8 @@ notmuch_new_command (void *ctx, int argc, char *argv[])
     for (i = 0; i < argc && argv[i][0] == '-'; i++) {
 	if (STRNCMP_LITERAL (argv[i], "--verbose") == 0) {
 	    add_files_state.verbose = 1;
+	} else if (strcmp (argv[i], "--no-hooks") == 0) {
+	    run_hooks = FALSE;
 	} else {
 	    fprintf (stderr, "Unrecognized option: %s\n", argv[i]);
 	    return 1;
@@ -833,6 +836,12 @@ notmuch_new_command (void *ctx, int argc, char *argv[])
     add_files_state.synchronize_flags = notmuch_config_get_maildir_synchronize_flags (config);
     db_path = notmuch_config_get_database_path (config);
 
+    if (run_hooks) {
+	ret = notmuch_run_hook (db_path, "pre-new");
+	if (ret)
+	    return ret;
+    }
+
     dot_notmuch_path = talloc_asprintf (ctx, "%s/%s", db_path, ".notmuch");
 
     if (stat (dot_notmuch_path, &st)) {
@@ -981,5 +990,8 @@ notmuch_new_command (void *ctx, int argc, char *argv[])
 
     notmuch_database_close (notmuch);
 
+    if (run_hooks && !ret && !interrupted)
+	ret = notmuch_run_hook (db_path, "post-new");
+
     return ret || interrupted;
 }

notmuch.1

@@ -85,7 +85,7 @@ The
 command is used to incorporate new mail into the notmuch database.
 .RS 4
 .TP 4
-.B new
+.BR new " [options...]"
 
 Find and import any new messages to the database.
 
@@ -118,6 +118,22 @@ if
 has previously been completed, but
 .B "notmuch new"
 has not previously been run.
+
+The
+.B new
+command supports hooks. See the
+.B "HOOKS"
+section below for more details on hooks.
+
+Supported options for
+.B new
+include
+.RS 4
+.TP 4
+.BR \-\-no\-hooks
+
+Prevents hooks from being run.
+.RE
 .RE
 
 Several of the notmuch commands accept search terms with a common
@@ -705,6 +721,38 @@ specify a date range to return messages from 2009\-10\-01 until the
 current time:
 
 	$(date +%s \-d 2009\-10\-01)..$(date +%s)
+.SH HOOKS
+Hooks are scripts (or arbitrary executables or symlinks to such) that notmuch
+invokes before and after certain actions. These scripts reside in
+the .notmuch/hooks directory within the database directory and must have
+executable permissions.
+
+The currently available hooks are described below.
+.RS 4
+.TP 4
+.B pre\-new
+This hook is invoked by the
+.B new
+command before scanning or importing new messages into the database. If this
+hook exits with a non-zero status, notmuch will abort further processing of the
+.B new
+command.
+
+Typically this hook is used for fetching or delivering new mail to be imported
+into the database.
+.RE
+.RS 4
+.TP 4
+.B post\-new
+This hook is invoked by the
+.B new
+command after new messages have been imported into the database and initial tags
+have been applied. The hook will not be run if there have been any errors during
+the scan or import.
+
+Typically this hook is used to perform additional query\-based tagging on the
+imported messages.
+.RE
 .SH ENVIRONMENT
 The following environment variables can be used to control the
 behavior of notmuch.

notmuch.c

@@ -127,6 +127,32 @@ static const char search_terms_help[] =
     "\n"
     "\t\t$(date +%%s -d 2009-10-01)..$(date +%%s)\n\n";
 
+static const char hooks_help[] =
+    "\tHooks are scripts (or arbitrary executables or symlinks to such) that\n"
+    "\tnotmuch invokes before and after certain actions. These scripts reside\n"
+    "\tin the .notmuch/hooks directory within the database directory and must\n"
+    "\thave executable permissions.\n"
+    "\n"
+    "\tThe currently available hooks are described below.\n"
+    "\n"
+    "\tpre-new\n"
+    "\t\tThis hook is invoked by the new command before scanning or\n"
+    "\t\timporting new messages into the database. If this hook exits\n"
+    "\t\twith a non-zero status, notmuch will abort further processing\n"
+    "\t\tof the new command.\n"
+    "\n"
+    "\t\tTypically this hook is used for fetching or delivering new\n"
+    "\t\tmail to be imported into the database.\n"
+    "\n"
+    "\tpost-new\n"
+    "\t\tThis hook is invoked by the new command after new messages\n"
+    "\t\thave been imported into the database and initial tags have\n"
+    "\t\tbeen applied. The hook will not be run if there have been any\n"
+    "\t\terrors during the scan or import.\n"
+    "\n"
+    "\t\tTypically this hook is used to perform additional query-based\n"
+    "\t\ttagging on the imported messages.\n\n";
+
 static command_t commands[] = {
     { "setup", notmuch_setup_command,
       NULL,
@@ -144,7 +170,7 @@ static command_t commands[] = {
       "\tInvoking notmuch with no command argument will run setup if\n"
       "\tthe setup command has not previously been completed." },
     { "new", notmuch_new_command,
-      "[--verbose]",
+      "[options...]",
       "Find and import new messages to the notmuch database.",
       "\tScans all sub-directories of the mail directory, performing\n"
       "\tfull-text indexing on new messages that are found. Each new\n"
@@ -159,8 +185,15 @@ static command_t commands[] = {
       "\tis delivered and you wish to incorporate it into the database.\n"
       "\tThese subsequent runs will be much quicker than the initial run.\n"
       "\n"
+      "\tThe new command supports hooks. See \"notmuch help hooks\" for\n"
+      "\tmore details on hooks.\n"
+      "\n"
       "\tSupported options for new include:\n"
       "\n"
+      "\t--no-hooks\n"
+      "\n"
+      "\t\tPrevent hooks from being run.\n"
+      "\n"
       "\t--verbose\n"
       "\n"
       "\t\tVerbose operation. Shows paths of message files as\n"
@@ -529,6 +562,10 @@ notmuch_help_command (unused (void *ctx), int argc, char *argv[])
 	printf ("\n");
 	printf (search_terms_help);
 	return 0;
+    } else if (strcmp (argv[0], "hooks") == 0) {
+	printf ("Help for <%s>\n\n", argv[0]);
+	printf (hooks_help);
+	return 0;
     }
 
     fprintf (stderr,