Arrays are key-value maps. We should reindex the array after a filter
since we are using the key and count to do array access in filterTags.
An example would be searching for "foo, bar", after the array filter,
our array is actually (0 -> foo, 2 -> bar) which will cause an error
when trying to access $searchtags[1].
* search type now carried by LinkDB in order to factorize code between different search sources.
* LinkDB->filter split in 3 method: filterSearch, filterHash, filterDay (we know what type of filter is needed).
* filterHash now throw a LinkNotFoundException if it doesn't exist: internal implementation choice, still displays a 404.
* Smallhash regex has been rewritten.
* Unit tests update
* Searching '-mytag' will now exlude all shaares with 'mytag' tag.
* All tags starting with a '-' are renamed without it (through the Updater).
* Unit tests.
Minor code changes:
* LinkDB->filter() can now take no parameters (get all link depending on logged status).
* tagsStrToArray() is now static and filters blank tags.
* contains methods designed to be run once.
* is able to upgrade the datastore or the configuration.
* is based on methods names, stored in a text file with ';' separator (updates.txt).
* begins with existing function 'mergeDeprecatedConfigFile()' (options.php).
* introduce class LinkFilter to handle link filter operation (and lighten LinkDB).
* handle 'private only' in filtering.
* update template to prefill search fields with current search terms.
* coding style.
* unit test (mostly move from LinkDB to LinkFilter).
PS: preparation for #358#315 and 'AND' search.
