unshelve: add help text on --interactive in verbose mode
This is a follow-up patch to rHG9eace8d6d537. This modifies the
help text of unshelve in verbose mode to mention the details
about `--interactive` flag.
Differential Revision: https://phab.mercurial-scm.org/D6676
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
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Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
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See https://mercurial-scm.org/ for detailed installation
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