Blender Git Loki

Merge branch 'master' into soc-2020-info-editor

# Conflicts:
# source/blender/windowmanager/intern/wm_files.c

LibOverride: Cleanup: Remove option to disable library overrides.

Code is mature enough now to not need this anymore, people who do not
want to use liboverrides can just not create them.

Cleanup: silence warnings

MSVC: Fix build error with the 8.1 SDK

shobjidl_core.h only exists in the windows 10 SDK in the 8.1
SDK ShObjIdl.h will have the definitions we need, which still
exists in the 10 SDK and implicitly includes shobjidl_core.h.

so ShObjIdl.h will work on both SDK versions.

EEVEE: Fix sky zenith bug

Careless use of acos() in spherical coordinates transformation was
deteriorating the precision near zenith (and nadir) and producing
glitchy pixels (best seen in longer focal lengths).

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D8266

Fix T78037: fresh install of blender 2.83.0 not able to save user startup file.

Simply remove that check ob userdef's themes, we are never read any
userdef from startup file anymore, so this check makes no more sense.

To be backported to 2.83.

Fix T76687: [Mantaflow] low domain transformation performance

Implemented G.moving suggestion from comments.

Fix broken shading in workbench

Build: make update support for git tags

Previously it only picked the appropriate version with the
blender-vX.XX-release branches.

Build: make update support for git tags

Previously it only picked the appropriate version with the
blender-vX.XX-release branches.

EEVEE: Rename default_world_frag.glsl to lookdev_world_frag.glsl

Also include cleanups of the world rendering logic.

Fix undefined behavior with background alpha

Python API: new RNA property `Screen.is_scrubbing`

This commit adds a new read-only boolean property `Screen.is_scrubbing`.

The related property `Screen.is_animation_playing` is set to `True` in
two situations:

- Animation is actually playing (for example via the Play button in the
timeline)
- The user is scrubbing through time (in the timeline, dopesheet, graph
editor, etc.)

To distinguish between these two cases, the property
`Screen.is_scrubbing` has been added.

Concept approved by @brecht.

VSE: Python API, allow creation of VSE Movie strips with missing file

It was already possible to create Sound and Image strips that reference
non-existing files. Now it's also possible to create Movie strips
referencing missing files via the Python API call
`Sequences.new_movie()`. In this case, the duration of the strip will be
set to 1 frame.

Note that this commit does not change anything in the user interface.

The Python API of the `MovieStrip` class is extended with a function
`reload_if_needed()`. This function only performs disk I/O if the movie
strip cannot produce frames, that is either when its filepath points to
a non-existing file, or when the video sequence editor has not been
shown yet (for example because it is in an inactive workspace).

This allows for the following:

```
import bpy

scene = bpy.context.scene
vse = scene.sequence_editor_create()

filepath = bpy.path.abspath('//demo.mkv')
strip = vse.sequences.new_movie("movie", filepath,
channel=2,
frame_start=47,
file_must_exist=False)
strip.frame_final_end = 327
```

This will create a new movie strip, even when `demo.mkv` does not exist.

Once `demo.mkv` has appeared at the expected location, either
`strip.reload_if_needed()` or `strip.filepath = strip.filepath` will
load it.

Differential Revision: https://developer.blender.org/D8257

Reviewed By: Sergey, ISS

LibOverride: add more polling checks to operators not supposed to work on overrides.

This is long work, we are still likely missing a lot of cases...

Cleanup: remove public unused function.

Fix T78855: Knife tool crashes when the geometry has no face

I don't see the need for a BVH Tree to have root but not have leafs.
But apparently this case is possible.

Optimization: Use dedicated function to restore customdata

Called when canceling a transform operation.

Cleanup: move unchanged condition out of loop

Fix Extrude Manifold losing original UV