This was a no-op previously, but this operation makes no sense.

The existing implementation has been utterly broken forever; I cannot
explain what it actually does, but it doesn't do what the
documentation says.

Use MoveRange() instead of MoveId().

Now, "+0" means "right after the current song" and "-0" means "right
before the current song".  Mnemonic: there are zero songs between the
current song and the newly added song.

A similar feature was present long ago in MPD, but was deprecated in
version 0.16 because the implementation was broken.  This commit
re-adds the feature in a way that's well-defined and not broken.

Close https://github.com/MusicPlayerDaemon/MPD/issues/1221

Validate early, so we avoid the rollback if an error occurs.

Skip the LookupRemoteTag() call if the MoveId() call fails.

Eliminates lots of implicit std::string temporaries.

This reverts commit 6ed4aff4.  The
Meson wrap is broken on non-x86, because it unconditionally includes
<cpuid.h> which is an x86 only header.

This way, URI schemes supported by arbitrary storage plugins are
allowed.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1270

Fixes crash bug.

This should translate to ACK_ERROR_ARG instead of ACK_ERROR_UNKNOWN.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1265

This way, we know whether we're explicitly "paused" or "not yet
activated because the ring buffer hasn't been filled yet".

Fixes the build with libexpat from Meson wrap.

Necessary since commit 6acf81d5

Allow DeferredEvents to call EventLoop::Break().

emplace already calls std::pair. No need for it again.

No need to emplace when calling std::make_shared.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

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

This eliminates all but one DeleteLocalRef() call.