The extra things `eval` does are all for code that runs
interactively. Because we just define a function, we don't need it.
This improves alias' performance by about 20-25% (0.783608s to 0.585585s
on about 500 aliases) and avoids triggering #3345.
The new --wraps functionality was breaking aliases of the form
`alias foo='bar baz'`. That is, aliases where the body is multiple
words. Extract the first word of the body and use that instead.
Use better errors for aliases with no name or no body.
Add the --wraps option to 'complete' and 'function'. This allows a
command to (recursively) inherit the completions of a wrapped command.
Fixes#393.
When evaluating a completion, we inspect the entire "wrap chain" for a
command, i.e. we follow the sequence of wrapping until we either hit a
loop (which we silently ignore) or the end of the chain. We then
evaluate completions as if the wrapping command were substituted with
the wrapped command. Currently this only works for commands, i.e.
'complete --command gco --wraps git\ checkout' won't work (that would
seem to encroaching on abbreviations anyways). It might be useful to
show an error message for that case.
The commandline builtin reflects the commandline with the wrapped
command substituted in, so e.g. git completions (which inspect the
command line) will just work. This sort of command line munging is
also performed by 'complete -C' so it's not totally without precedent.
'alias will also now mark its generated function as wrapping the
'target.
