Remove delete_after_merge option

[asvoboda]

GH now supports automatically deleting branches (as of 2.22.4), so Bulldozer no longer needs to support the delete_after_merge option.

We can probably remove the supporting code and leave the option around, if we don't want to break any config changes:

bulldozer/bulldozer/merge.go

Lines 215 to 216 in a495289

	if mergeConfig.DeleteAfterMerge {
	attemptDelete(ctx, pullCtx, head, merger)

[anishagg17]

Hi @asvoboda, I would like to work upon this issue if there's no one assigned to this one

[asvoboda]

Sure thing. Feel free to submit a PR and we can review.

[xero-timothy]

Can I please object to this? Github Enterprise doesn't support this yet, and this is a nice feature for those of us stuck on GHE.

[asvoboda]

Hey @xero-timothy,

Your concern is one of the reasons we haven't yet merged this change. GHE_ does_ support the delete-after-merge option natively as of 2.21.0. However, based on our internal testing the feature was broken in 2.21.3 and not fixed until 2.22.4.

As it stands, it probably doesn't hurt to keep this redundant feature around.