Correct cursor jumping from line 2 to line 1 due to line 1 being empty.

[msftrncs]

Correct newline search in GetBeginningOfLinePos() (HOME) and InsertLineAbove() (CTRL-ENTER) (by using GetBeginningOfLinePos()) to not ignore first character in the buffer which might be a new line.

Manifests as cursor jumps to line 1, because line 1 is blank, when triggered with cursor anywhere on line 2.

Fixes #1107.
Fixes #1109.

[msftrncs]

I just noticed, a similar issue when pressing home, for which this very same code occurs in GetBeginningOfLinePos(). I could instead fix the issue there, and alter InsertLineAbove() to utilize GetBeginningOfLinePos().

[lzybkr]

It'd be good to add a test.

If you are extra motivated, you could add a property based test using FsCheck. It seems property based testing might be a good way to catch cases like this without writing too many tests.

[msftrncs]

Test added.

Any input on this?

I just noticed, a similar issue when pressing home, for which this very same code occurs in GetBeginningOfLinePos(). I could instead fix the issue there, and alter InsertLineAbove() to utilize GetBeginningOfLinePos().

I have this code change ready, including test for it as well.

[msftrncs]

Closing and reopening to retrigger the CI.

[lzybkr]

@msftrncs - Good catch finding the duplicated code - your proposed fix sounds perfect.

[msftrncs]

I have updated the commits so that GetBeginningOfLinePos() gets the fix, and InsertLineAbove() uses GetBeginningOfLinePos(), and including tests for both issues fixed by this.

[msftrncs]

Updated Title and PR to reflect the changes in the commits.