Rename yarn clean (#52)

* Initial RFC: rename yarn clean

* Rename rename-yarn-clean.md to 0000-rename-yarn-clean.md

* Fix a proposed name

* Delete a leftover paragraph

* Change new name to autoclean

Author: jimmytheneutrino

text/0000-rename-yarn-clean.md

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+- Start Date: 2017-03-13
+- RFC PR: (leave this empty)
+- Yarn Issue: (leave this empty)
+
+# Summary
+
+Rename `yarn clean` command.
+
+# Motivation
+
+1. People might expect `yarn clean` to do a different thing (to clean build artifacts) 
+than it actually does 
+(cleans node modules of some files and sets the system to clean it automatically in the future). 
+This is a very natural expectation because it is usually possible to do, e.g., 
+`yarn watch`, `yarn dist`, and of course, `yarn clean` seems like a logical command 
+(compare with gradle clean, mvn clean, gulp clean).
+
+ Next, when `yarn clean` is executed a user realizes that it is not the correct command 
+but it does not seem to do anything drastic (probably just cleans some yarn caches) and 
+forgets about it. 
+(Of course, the right thing to do would be to look at https://yarnpkg.com/en/docs/cli/clean instead.) 
+The result often is that the project is broken and the bug is hard to detect. 
+There are a lot of such bugs in this project and more elsewhere (example: twbs/bootstrap-sass#1097).
+
+ The name is confusing and the best way to stop confusion seems to be renaming the command.
+
+2. Also, it is nice to be able to run a user-defined `yarn clean` if you already can run a user-defined `yarn build`.
+
+# Detailed design
+The command is to be renamed to `autoclean`.
+
+Next, `clean` should be available for redefinition by user scripts.
+
+It should be more or less safe after that to produce an error in a standard way when `clean`
+is executed but the user script is missing. This is because the command is not usually run
+during a build but is mostly executed manually and its state persisted in cvs as a `.yarnclean` file.
+
+
+# How We Teach This
+The documentation should only reflect the change of the command name.
+
+Release notes should provide a note about a possible breaking change.
+
+# Drawbacks
+
+We should not do this if yarn does not want to promote using `yarn command`
+for user defined scripts. Note that then the existing usage of such commands 
+should also be deprecated.
+
+# Alternatives
+1. Produce big and nice warnings when the command is used 
+and on subsequent installation of modules (listing cleaned/ignored files).
+(This does not solve point 2. of the Motivation.)
+2. Deprecate `yarn command` for user-defined scripts. (So that only `yarn run command` is supported.)
+3. Deprecate running user-defined commands through yarn altogether (and optionally provide
+a different default command for running user-scripts, e.g., `yarun`).
+4. Some alternative proposed new name candidates are:
+`delete-module-bloat`, `delete-package-assets`, `remove-module-files`,
+`enable-advanced-auto-disk-space-optimizations`, `prune`, `pruneModules`,
+`strip`, `shrink`, `stripModules`, `shrinkModules`, `cleanModules`,
+`stripPackages`, `yarn-clean`.