1. Added missing commands and arguments.
2. Removed alternative spelling of some commands (e.g. clear-cache|clearcache) since a choice of spelling is not really useful for completion.
3. Fixed a typo: np-ansi → no-ansi.
4. Removed redundant backslash in front of $COMPOSER_HOME.
The updated completion was initially generated using the bamarni/symfony-console-autocomplete package and then incorporated into the existing code.
This patch adds completion for the update subcommand, that is, when the
user types in `composer update <tab>`.
The code depends on python for the json parsing. I'm not sure if this
is appropriate or if there is a fish-native way to parse json data.
Use suggestions for remove subcommand.
Add suggestions for why, why-not and depends.
Add why/why-not suggestion.
This is already done by fish before calling the completion.
It breaks completion with combiners (#2025) and also with wrappers.
(This does not include git because that's better solved in #2145)
