rustc: Start "stabilizing" some flags

[alexcrichton]

This commit shuffles around some CLI flags of the compiler to some more stable
locations with some renamings. The changes made were:

• The -v flag has been repurposes as the "verbose" flag. The version flag has
  been renamed to -V.
• The -h screen has been split into two parts. Most top-level options (not
  all) show with -h, and the remaining options (generally obscure) can be
  shown with --help -v which is a "verbose help screen"
• The -V flag (version flag now) has lost its argument as it is now requested
  with rustc -vV "verbose version".
• The --emit option has had its ir and bc variants renamed to llvm-ir
  and llvm-bc to emphasize that they are LLVM's IR/bytecode.
• The --emit option has grown a new variant, dep-info, which subsumes the
  --dep-info CLI argument. The --dep-info flag is now deprecated.
• The --parse-only, --no-trans, --no-analysis, and --pretty flags have
  moved behind the -Z family of flags.
• The --debuginfo and --opt-level flags were moved behind the top-level -C
  flag.
• The --print-file-name and --print-crate-name flags were moved behind one
  global --print flag which now accepts one of crate-name, file-names, or
  sysroot. This global --print flag is intended to serve as a mechanism for
  learning various metadata about the compiler itself.
• The top-level --pretty flag was moved to a number of -Z options.

No warnings are currently enabled to allow tools like Cargo to have time to
migrate to the new flags before spraying warnings to all users.

cc #19051

[alexcrichton]

cc @brson, @cmr, @nick29581

[sinistersnare]

Not a huge fan of -v being verbose. I think that if people want verbose, they might as well just type --verbose.

[emberian]

Looks as discussed, 👍

[emberian]

@sinistersnare existing tools aren't consistent about the treatment of -v, -V, --version, and --verbose. This brings us in line with Cargo and some other compilers, including cc.

[sinistersnare]

Ah ok :) sounds good, +1 then

[mdinger]

Looks like this fixes #17938 and rust-lang/cargo#690

[pnkfelix]

cc me

[pnkfelix]

The summary claims that --pretty was moved to a number of -Z flags, but not all functionality currently located there was preserved. I suspect everything will pass in this PR as-is, because it does not actually remove "pretty" from the optgroups() result; it just has a comment saying that it and a number of other options are deprecated. (And therefore if I understand correctly, the --pretty flowgraph tests in src/tests/run-make will still run; they are just using an option that has been silently deprecated without a replacement.)

I have proposed -Z unstable-options in PR #19964 as a path towards keeping some getopts-based options that we do not want to be part of the stable interface for our users.

[pnkfelix]

hey @alexcrichton , why did you put in this code that, AFAICT, is the identity function on Option<T> ?

[alexcrichton]

Hm I think I forgot to remove this after some other refactoring in this area, feel free to remove though!

[pnkfelix]

@alexcrichton do we have a good place to discuss moving options around (either out of the short groups, or into the unstable-options that I am planning to land today)? In particular, I would imagine --target, --print, --crate-name, and --cfg could all be moved out of the short group.

[alexcrichton]

I'm fine with chatting on IRC, I was personally thinking that all of those options would stay at the top-level, but they're certainly flexible!

[pnkfelix]

IRC discussion here: https://botbot.me/mozilla/rust-internals/2014-12-22/?msg=28137683&page=7