Use the `reason` attribute to be able to handle `UsageError` subclasses
more uniformly and simplify logic in `brew.rb` to handle them together.

Instead of always printing the generic help text, print command-specific
help if it is available and a command raised the `UsageError` exception.
Put the error message underneath the help text (was above) to avoid that
it scrolls off the screen.

Thereby fix a regression where handling the invalid usage would fail to
access `ARGV.usage` removed in c6536066.

Turns out making `empty_argv` a boolean argument for `Homebrew.help` was
not the best idea and having command-to-path mapping and help extraction
in a single method is not flexible enough.

Also only complain about missing help text when `HOMEBREW_DEVELOPER=1`
and otherwise just print the generic help text.

Format the usage examples more consistently (particularly parentheses
instead of square brackets where one of several alternatives has to be
picked). And add the now much more useful `brew help <command>`.

Closes #113.

Signed-off-by: Martin Afanasjew <martin@afanasjew.de>

This implies that `--version` is treated in most places like a regular
command, e.g. being suggested in shell completion. Also fix the help
text that claimed output goes to standard error, while it actually goes
to standard output.

In `Library/Homebrew/test/`:

test_integration_cmds.rb:431: warning: (...) interpreted as grouped expression
test_integration_cmds.rb:502: warning: (...) interpreted as grouped expression
test_integration_cmds.rb:507: warning: (...) interpreted as grouped expression
test_integration_cmds.rb:585: warning: (...) interpreted as grouped expression
test_integration_cmds.rb:709: warning: (...) interpreted as grouped expression
test_integration_cmds.rb:710: warning: (...) interpreted as grouped expression
test_integration_cmds.rb:711: warning: (...) interpreted as grouped expression

Library/brew.rb:108: warning: `*' interpreted as argument prefix

Library/Homebrew/cmd/man.rb:44: warning: assigned but unused variable - commands

Closes #116.

Signed-off-by: Xu Cheng <xucheng@me.com>

Closes #115.

Signed-off-by: Xu Cheng <xucheng@me.com>

* without `default_remote`, `CoreTap#install` won't be able to tell
  whether user has passed to custom remote to it.
* simplify some part of logics

* remote check requires `git` installed.
* Do not perform check if user does not passing remote explicitly.

Fixes #108

This reverts commit 2caf7b76.

Library/Homebrew/dev-cmd/linkage.rb:113: warning: shadowing outer local variable - label

Library/Homebrew/cmd/man.rb:44: warning: assigned but unused variable - commands

Noted, `brew tap foo` will not fail if the tap is already installed.

This is to avoid TapFormulaAmbiguityError.
We should load formula based on what we installed,
rather than just name.

Pulls 'brew linkage' in to main brew repo as a dev-cmd, and has test-bot
use it to detect dylib breakage, which usually means a revision bump is
needed. Checks all dependents, not just those with a 'test do' block
defined, since we can do this without formula support.

Closes #107.

Signed-off-by: Andrew Janke <andrew@apjanke.net>

Fixes mistydemeo/tigerbrew#186.

Closes #110.

Signed-off-by: Misty De Meo <mistydemeo@github.com>

https://github.com/Homebrew/brew/commit/e70a3552d3faddd0afd2535a03c31b8c50be901a seems to have
exacerbated the problem where taps stick around and then `brew uses` gets executed
on a whole host of taps, which is currently breaking almost every PR for formulae
that would be used cross-tap, as well as causing lengthier CI builds.

Examples from the last week or so include sqlite, V8, protobuf, and so on. Whilst it
may be true that cross-tap formulae failing can show problems that need looking at,
a lot of the time the failures are unrelated to the build in question and just
leave contributors confused on what needs to be done, or why their PR is failing
for something that seems entirely unrelated.

You can see the taps failing to vanish locally by doing something like:

```
brew tap homebrew/fuse
brew tap homebrew/versions
cd $(brew --prefix) && git clean -ffdx --exclude=/Library/Taps/
brew tap
...
homebrew/core
homebrew/fuse
homebrew/versions
```

This is a very simple proposal to handle the problem, but there's no real reason
I couldn't write this functionality into untap itself and then we call that in
test-bot. Just didn't necessarily want to jump immediately to expanding the untap
command to solve what is more-or-less a CI problem.

Also enables sandbox for --interactive and --debug use of install
and test, using automatic retention.

Closes #66.

Signed-off-by: Andrew Janke <andrew@apjanke.net>

This is a nicer error message than the `exec` failing at a later stage.

Showing help makes sense for `brew help <command>`, but showing it for
`brew <command> help` is undesirable and prevents all commands from
accepting a named argument `help` (formula, tap, file name, etc.).

All other help flags are still detected before *and* after the command.

Closes #103.

Signed-off-by: Martin Afanasjew <martin@afanasjew.de>

Also remove related helper method `Homebrew.help_s`.

Keep the footprint of `brew.rb` small. Handle fetching/displaying an
appropriate help text (taking into account various external conditions)
in the `help` command.

Closes #101.

Signed-off-by: Martin Afanasjew <martin@afanasjew.de>

Don't search for alternatives if formula was found, but has issues, as
this will create confusing output, particularly for contributors working
on a formula file.

Present a more helpful error message if a formula file was loaded, but
the class(es) therein didn't match the expected formula class name.

Closes #102.

Signed-off-by: Martin Afanasjew <martin@afanasjew.de>