Fallout from fix of bundler path gems always causing re-resolve (https://github.com/bundler/bundler/pull/4618)

gistfile1.txt

* Even with no changes to the gemspecs for path based gems, bundler will always
  re-resolve.

* After fixing above, the following issues were uncovered because the re-resolve
  was masking these problems.

1) When you have a path with multiple gemspecs in subdirectories:
  When bundler creates a Bundler::Source::Path object at the toplevel directory,
  it creates gem specifications for each gemspec but the path to the gemspec uses
  the toplevel path and not the nested path.

  gem
    foo
      foo.gemspec
    bar
      bar.gemspec

  path "gem/" do
    gem "foo"
    gem "bar"
  end

  Or:
  gem "foo", :path => "gem/"
  gem "bar", :path => "gem/"


  Bundler::Source::Path.new('path' => 'gem').specs =>
   [Gem::Specification foo, 'path' => 'gem', Gem::Specification bar, 'path' => 'gem']]

  It should be something like this:
  Bundler::Source::Path.new('path' => 'gem').specs =>
   [Gem::Specification foo, 'path' => 'gem/foo', Gem::Specification bar, 'path' => 'gem/bar']]

  * dependencies_for_source_changed? looks for dependencies and locked dependencies
    based on the source and because we have incorrectly marked multiple dendendencies
    with the same source path, and therefore compare incorrectly... words


2) Bundler::Source::Path#specs always goes to the filesystem to retrieve specs.
  When a Path is created in the LockfileParser, it does not directly populate the
  specs for that source from the information in the lockfile.

  p = Bundler::Source::Path.new
  LazySpec.new("foo", "1.0").source = p
  LazySpec.new("bar", "1.0").source = p

  p.specs # Goes out to the filesystem which may have changed so might not match foo and bar

  Later, when we try to compare the lockfile to the filesystem to detect changes,
  we end up comparing the filesystem dependencies to itself, thus yielding "no changes detected."

* converge_locked_specs is responsible for using the parsed Gemfile.lock and removing
  any entries from the lock which cannot be re-used because they have changed.

* nothing_changed? should be detecting any changes to the various gem types and
  allow bundler to re-resolve on top of the partial tree we obtained from the
  converge_locked_specs.  When converge_locked_specs returns a partial tree with
  path level changes removed, we'd expect nothing_changed? to return false but
  instead it returns true because of bug #2.  This causes a partial tree to be
  written to the lockfile.