Without clearing all `in_playlist` flags, the songs will never be
revealed again if they were hidden once by a CUE sheet, not even after
the CUE sheet gets deleted or modified.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1784

Fixes assertion failure if the ZIP file contains a path that begins
with a slash.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1793

Fixes hide_playlist_targets not working after server restart

Currently, `hide_playlists_targets` works by skipping songs with
`in_playlist` value set to true in
[`Directory::Walk`](https://github.com/MusicPlayerDaemon/MPD/blob/a57bcd02382947abbd961594cdf00302c0c7866a/src/db/plugins/simple/Directory.cxx#L237). But
`in_playlist` is not stored and only updated in
[`UpdateWalk::PurgeDanglingFromPlaylists`](https://github.com/MusicPlayerDaemon/MPD/blob/a57bcd02382947abbd961594cdf00302c0c7866a/src/db/update/Playlist.cxx#L139),
which will only be executed while updating DB.

This causes the problem that playlist target songs are correctly
hidden after database update, but will remain visible after mpd server
restarted. This pr solves the problem by storing `in_playlist` value
of songs into the `SimpleDatabase` file.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

shorter
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Fixes "searchaddpl" bug emitting bogus error "Bad position".

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1338

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1352

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1328

Add an option to the UPnP database plugin to configure which interface
is used by upnp to discover servers.

upnp by default selects the first interface that is not loopback, which
in some cases might not be the desired interface. For example if wanting
to access a DLNA server over a VPN connection.

The "interface" option can now be set to the name of the desired
interface to achieve this.

The default behaviour remains unchanged.

Adds the Interface Name as an argument to the *Init functions to make it
possible to select which interface is used by upnp to detect servers.

Currently "nullptr" is passed in to let the upnp library select an
interface, as before.

Unlike GetFilenameSuffix(), uri_get_suffix() removes the query string
first, which breaks file names with question marks in the name.
Therefore, uri_get_suffix() shall only be applied to remote URIs.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1316

Regression by commit 2d8847f4

This reduces duplicates in the music database by hiding the original
song file when it is referenced by a CUE sheet.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1275

This reverts commit 9200fa6d.  It was
wrong because it works only if the target song has already been
scanned.

make_pair is an old C++98 function that can be replaced by modern
shorter constructs.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

These should be equivalent anyway.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

loop is wrong anyway. It's missing a break;
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1019