Dont treat Mercurial repos as an error

[jayvdb]

In a similar vein as #279 , I see the following for https://crates.io/crates/oorandom

warning: failed to clone `https://hg.sr.ht/~icefox/oorandom`: [
    "fatal: repository 'https://hg.sr.ht/~icefox/oorandom/' not found\n",
]
...
oorandom (https://hg.sr.ht/~icefox/oorandom is uncloneable)

It is maintained, recently fixing the metadata - c.f. https://todo.sr.ht/~icefox/oorandom/8

While I can appreciate that there may not be much benefit in adding support for Mercurial repos, and a processing warning is useful, the crate should be "unmaintained" simply because it is using Mercurial.

A list of hg hosting platforms can be found at https://wiki.mercurial-scm.org/MercurialHosting . Some like https://hg.sr.ht/ and https://hg.mozilla.org/ and http://hg.code.sf.net/ include "hg." prefix which could be used to detect it.

However others dont have an easy way to detect e.g. https://crates.io/crates/bytes-cast

[smoelius]

Note to self: the report comes from here: https://github.com/trailofbits/cargo-unmaintained/blob/1994fac346cdc06705fe8b6981136d68734beb62/src/main.rs#L458

That is, to be considered maintained, a package must be a member of its named repository. And to determine whether that is the case, cargo-unmaintained must clone the repository.