make complaints about unrecognized keywords more verbose

tell the user in what section the keyword appeared, as that may help
spotting mistakes like stray empty lines.

src/config.c

@@ -425,7 +425,8 @@ load_config( const char *where )
 					if (*++p)
 						channel->boxes[fn] = nfstrdup( p );
 				} else if (!getopt_helper( &cfile, &cops, channel )) {
-					error( "%s:%d: unknown keyword '%s'\n", cfile.file, cfile.line, cfile.cmd );
+					error( "%s:%d: keyword '%s' is not recognized in Channel sections\n",
+					       cfile.file, cfile.line, cfile.cmd );
 					cfile.err = 1;
 				}
 			}
@@ -476,7 +477,7 @@ load_config( const char *where )
 				}
 				else
 				{
-					error( "%s:%d: unknown keyword '%s'\n",
+					error( "%s:%d: keyword '%s' is not recognized in Group sections\n",
 					       cfile.file, cfile.line, cfile.cmd );
 					cfile.err = 1;
 				}
@@ -511,7 +512,7 @@ load_config( const char *where )
 		}
 		else if (!getopt_helper( &cfile, &gcops, &global_conf ))
 		{
-			error( "%s:%d: unknown section keyword '%s'\n",
+			error( "%s:%d: '%s' is not a recognized section-starting or global keyword\n",
 			       cfile.file, cfile.line, cfile.cmd );
 			cfile.err = 1;
 			while (getcline( &cfile ))

src/driver.c

@@ -49,7 +49,7 @@ free_generic_messages( message_t *msgs )
 }
 
 void
-parse_generic_store( store_conf_t *store, conffile_t *cfg )
+parse_generic_store( store_conf_t *store, conffile_t *cfg, const char *type )
 {
 	if (!strcasecmp( "Trash", cfg->cmd )) {
 		store->trash = nfstrdup( cfg->val );
@@ -72,7 +72,7 @@ parse_generic_store( store_conf_t *store, conffile_t *cfg )
 		}
 		store->flat_delim = nfstrdup( cfg->val );
 	} else {
-		error( "%s:%d: unknown keyword '%s'\n", cfg->file, cfg->line, cfg->cmd );
+		error( "%s:%d: keyword '%s' is not recognized in %s sections\n", cfg->file, cfg->line, cfg->cmd, type );
 		cfg->err = 1;
 	}
 }

src/driver.h

@@ -276,7 +276,7 @@ struct driver {
 uint count_generic_messages( message_t * );
 void free_generic_messages( message_t * );
 
-void parse_generic_store( store_conf_t *store, conffile_t *cfg );
+void parse_generic_store( store_conf_t *store, conffile_t *cfg, const char *type );
 
 store_t *proxy_alloc_store( store_t *real_ctx, const char *label );
 

src/drv_imap.c

@@ -3529,10 +3529,11 @@ imap_parse_store( conffile_t *cfg, store_conf_t **storep )
 				}
 				store->delimiter = cfg->val[0];
 			} else
-				parse_generic_store( &store->gen, cfg );
+				parse_generic_store( &store->gen, cfg, "IMAPStore" );
 			continue;
 		} else {
-			error( "%s:%d: unknown/misplaced keyword '%s'\n", cfg->file, cfg->line, cfg->cmd );
+			error( "%s:%d: keyword '%s' is not recognized in IMAPAccount sections\n",
+			       cfg->file, cfg->line, cfg->cmd );
 			cfg->err = 1;
 			continue;
 		}

src/drv_maildir.c

@@ -1913,7 +1913,7 @@ maildir_parse_store( conffile_t *cfg, store_conf_t **storep )
 				cfg->err = 1;
 			}
 		} else
-			parse_generic_store( &store->gen, cfg );
+			parse_generic_store( &store->gen, cfg, "MaildirStore" );
 	if (!store->inbox)
 		store->inbox = expand_strdup( "~/Maildir" );
 	if (store->sub_style == SUB_MAILDIRPP && store->gen.path) {