Make helm-projectile-ag provide a default search input like helm-proj…

[Chobbes]

…ectile-grep.

When using helm-projectile-grep the search term will automatically be populated with the symbol at point, or the selected region. These changes make helm-projectile-ag do the same thing.

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[Chobbes]

Apparently there is already an option for this within helm-ag itself...

(setq helm-ag-insert-at-point 'symbol)

That said, I do wonder if it should follow helm-projectile-set-input-automatically. The documentation for helm-projectile-set-input-automatically does mention this:

Applies to ‘helm-projectile-grep’ and
‘helm-projectile-ack’ only. If the ‘helm-ag’ package is
installed, then automatic input behavior for ‘helm-projectile-ag’
can be customized using ‘helm-ag-insert-at-point’.

So maybe this has all been considered before... Still, it seems an odd default for helm-projectile-ag. Thoughts?