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Changes between Initial Version and Version 1 of Ticket #1807, comment 3

initial	v1
4	4	Because:
5	5	- there's no ticket proposing to allow an {{{http://...}}} prefix for Tahoe URIs, and I don't think we want that.
6		- the human encoding parsers don't implement #884 or #885. They partially implement #942, but inconsistently, for example most of the "{{{:}}}" characters can be replaced by "{{{%3A}}}" (matched case-sensitively, which is wrong), but the one before an MDMF extension field cannot. This is because ~~#942 is implemented~~ in a suboptimal way: we should be %-unencoding the whole Tahoe URI rather than treating "{{{:}}}" as a special case.
	6	- the human encoding parsers don't implement #884 or #885. They partially implement #942, but inconsistently, for example most of the "{{{:}}}" characters can be replaced by "{{{%3A}}}" (matched case-sensitively, which is wrong), but the one before an MDMF extension field cannot. This is because the human encoding implementation approaches this in a suboptimal way: we should be %-unencoding the whole Tahoe URI rather than treating "{{{:}}}" as a special case.
7	7	- making this change has very little regression risk because it is only dead code that is being removed.
8	8	- most of the work of implementing #942, #884, and #885 is in adding and repairing tests, the non-test code changes are straightforward. So not much effort is actually saved by reusing the human encoding code.