The comment-keeping summer.yaml edit refused a flow-style plugins list
(plugins: [{id: a, module: b}]) that plugin:add used to handle with a
full rewrite. The edit now replaces an inline list, over one or several
lines, with a block list of its items plus the new ones and keeps every
other line. A list it cannot edit in place (a tagged one, say) falls
back to the full SaveManifest rewrite with a note that the comments were
not kept. plugin:install gets the same behaviour.
- TestPluginDirs and TestEffectiveFramework over go list JSON fixtures and
git checkouts; TestResolveInstall against an in-memory registry;
TestAppendManifestPlugins for the in-place summer.yaml edit
- fix: a package of the application's own module was reported as a
submodule with the application's git describe; it is in-app (local)
- fix: summer.yaml items written as '- id:' keep their spacing when
plugin:add or plugin:install appends to them
