[DOC] Changes to examples

[BurdetteLamar]

Uses tree in examples for FileUtils.cp_lr.
Retains File.exist? only when the result will be true; otherwise changes to File.file? or File.directory?, which is more precise.

[peterzhu2118]

I think indentation is off by one on this line.

[BurdetteLamar]

Fixed.

[peterzhu2118]

If you're calling the tree method, you need to make the arguments strings.

Suggested change

	# tree src0
	# tree('src0')

[BurdetteLamar]

Fixed (five places).

[peterzhu2118]

I’ve noticed that the output of the tree command in the code block makes it difficult to read the code because there’s no syntax highlighting. I think we should change it so that the output of the tree command is a comment. See the screenshot for the difference it makes.

Before:

After:

[BurdetteLamar]

I've noticed ....

Fixed at cp_lr with slight difference from your suggested format. If ok, I'll fix the others.

[peterzhu2118]

👍 I like this new format. Thank you.

[BurdetteLamar]

👍 I like this new format. Thank you.

Much better! Thanks for the suggestion. All fixed now.

[peterzhu2118]

Looks good!