Copy all when markdown document is collapsed is incomplete

[sixeyes]

We have written
Issue Type: Bug

I tried to attach the document but .md isn't allowed. Tried to attach as .txt but it failed, so it's inline.

If the document is collapsed (Ctrl+K, Ctrl+0) and Ctrl+A to select all, the copied text does not include the WaveRecord onwards, it is only copied as far as the #Data Structures (line 6)

# (APIBlueprint document)

# Introduction
This is my introduction

# Data Structures

## WaveRecord (object)

+ mailingId: 103 (number, required) - The mailing identifier.
+ waveId: 253 (number, required) - The wave identifier.
+ name: `Initial Test` (string, required) - The wave name.
+ portion: 500 (number, required) - The wave portion of the mailing (1 - 10000), 10000 represents the whole mailing.
+ status: `Processed` (enum, required) - The wave status.
    + Members
        + `Draft` - The wave has been created but not queued.
        + `Processed` - The wave has been processed.
        + `Queued` - The wave has been queued but not processed.
+ createDate: `2016-07-30T16:28:22` (string, required) - The create date (UTC).
+ modifyDate: `2016-07-31T07:49:18` (string, required) - The last modified date (UTC).

VS Code version: Code 1.39.2 (6ab5985, 2019-10-15T15:35:18.241Z)
OS version: Windows_NT x64 10.0.18362

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-4440 CPU @ 3.10GHz (4 x 3100)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software oop_rasterization: unavailable_off protected_video_decode: unavailable_off rasterization: unavailable_off skia_deferred_display_list: disabled_off skia_renderer: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	17.58GB (8.30GB free)
Process Argv
Screen Reader	no
VM	100%

Extensions (5)

Extension	Author (truncated)	Version
vscode-guid	hea	1.4.19
apib	Jar	0.0.2
csharp	ms-	1.21.5
vscode-apielements	vnc	0.6.7
maple	yjt	1.2.8

(9 theme extensions excluded)

the needed data into your clipboard because it was too large to send. Please paste.

[aeschli]

Duplicate of #41744