Restore npm 6 ability to install one package

accepted/0000-install-single-package.md

@@ -0,0 +1,32 @@
+# Restore NPM 6 ability to install one package
+
+## Summary
+
+With npm@6, it was possible to install a single package. [This is no longer the case with npm@7](https://github.com/npm/cli/issues/3023).
+
+## Motivation
+
+My particular motivation is that in a monorepo, most of my projects use the same set of core dependencies, with only one or two specific dependencies for each project. I used to be able to install the core deps in the monorepo root, and only the specific deps in each project. The common ones were found in `../node_modules`. This massively reduced the install time and disk space usage, without having to resort to iffy symlinking via tools like `pnpm`.
+
+Besides myself, there have been many Q&As about this ability on StackOverflow ([1](https://stackoverflow.com/questions/52786695/npm-install-always-installs-everything-from-package-json), [2](https://stackoverflow.com/questions/49732031/npm-install-single-package-without-rest-of-dependencies), [3](https://stackoverflow.com/questions/22420564/install-only-one-package-from-package-json/65233880#65233880)), which suggests [significant](https://en.wikipedia.org/wiki/1%25_rule_(Internet_culture)) general demand for the feature.
+
+## Detailed Explanation
+
+A flag like `npm install <package> --only` could drive installing only the specified package.
+
+## Rationale and Alternatives
+
+One alternative would be to install everything from `package.json`, then try to figure out repeated dependencies and delete those directories. Besides being very cumbersome, this would *increase* the install time.
+
+Another one would be not declaring common dependencies at all in `package.json`.
+
+## Implementation
+
+
+## Prior Art
+
+npm@6
+
+## Unresolved Questions and Bikeshedding
+
+See https://github.com/npm/cli/issues/3023.