Setting DEBUG/QUIET environment variable to the empty string now acts
the same as unsetting it. Unsetting is not always easy/possible.

changed include files were not properly picked up by `erlc_compiler`
in cases where they were in directories relative to the application
source and not the current working dir of rebar3

fixes #1199

partially addresses #1184

- The configured stuff in rebar3 takes precedence over the ENV
- The env is then chosen

This required moving the reporting functions to rebar_base_compiler but
since this was already done for error_tuple, this seems to make sense.

Paths are also reformatted for warnings in erlc files.

This will allow us to eventually change the default type without it
looking ridiculous.

The previous iteration of the patch worked somewhat by accident. After
digging in and figuring out why the two dep sources are the way they
are, the patch is now properly working with a well-documented
explanatiion inline.

Formatted errors can accidentally contain substrings which are control
sequences for io:format/2. This is a naive attempt to handle such cases.

One example is running xref on the following module
(assuming module m does not exist)

```
-module(handle_error).

-export([f/0]).

f() -> m:'bobby~stables'().
```

```
$ rebar3 xref
===> Verifying dependencies...
===> Compiling myapp
===> Running cross reference analysis...
escript: exception error: bad argument
  in function  io:format/3
     called as io:format(<0.23.0>,
                         "\e[0;31m===> \e[1mWarning: handle_error:f/0 is unused export (Xref)\nWarning: handle_error:f/0 calls undefined function m:bobby~stables/0 (Xref)\n\n\e[0m\e[0m",
                         [])
  in call from rebar3:handle_error/1 (/Users/gomoripeti/git/rebar3/_build/default/lib/rebar/src/rebar3.erl, line 279)
```

This adds support for their format both on the first read and when
looking for modifications to dependencies.

fix issue #1185 git working directory issues due to command line options in Windows

closes #1057 and #1179

By default rebar3 displays compiler sources as absolute paths in their
original location, which is under the build dir.

This change introduces an option 'compiler_source_format' to format
sources in two alternative ways:

    relative
    absolute

When either 'relative' or 'absolute' are specified, the file is
resolved to its original location when it is a link. When 'relative'
is specified, the path is displayed relative to the current working
directory. When 'absolute' is specified, the path is absolute.

The default value is 'unchaged' which leaves the compiler source
unchanged.

This is arguably too flexible as I suspect most people would opt for
'relative' all the time - it's the most compact representation of the
file and is sufficient to find the source given cwd. The change
however is meant to introduce the change gradually, preserving
existing behavior and giving users a choice for formats.

In time perhaps the default can be changed to 'relative' - but still
allowing users to revert to the other two options ('absolutel' and
'unchanged') as needed.

Dependent libs is required for some module when cover compiling.
So all dependencies should be available on code path.

This fixes #1148 issue.

Allows `pre_hooks` and `post_hooks` to fire for the `edoc` provider.

Somehow swapping the tty handler once more fixes everything. I guess we
were missing a step somehow.

The sys.config loading in the shell command did not implement recursion
and thus processed the file different from a `erl -config cfg/path`.

Instead of reading every time that rebar_dir:global_cache_dir/1 is
called

When an app contains one of the modules we can't afford to get upgraded
without breakage (i.e. erlware_commons, providers, getopt), skip
reloading that application from the rebar3 agent, such that it can keep
on working in subsequent calls.

Blacklisted:

- erlware_commons (broke on ec_cmd_log)
- providers (core to functionality)
- cf (useful to not explode on colors)
- cth_readable (only used for CT suites, but incompatibilities may break
  whole runs)

I've tried to compile project with git in .app.src vsn
Project was tagged as 1.0.0, but resulting .app vsn becomes 1.0.0+build.6.reff0aec24

```git lg
* f0aec24 - (80 минут назад) Fixed ct — Kozlov Yakov (HEAD -> master, tag: 1.0.0, origin/master)
... 5 commits before
```

```
$ git log --oneline --no-walk --tags --decorate
f0aec24 (HEAD -> master, tag: 1.0.0, origin/master) Fixed ct
```

I've found that `HEAD -> master` doest match pattern in [rebar_git_resource](https://github.com/erlang/rebar3/blob/master/src/rebar_git_resource.erl#L204)

This commit moves the handling of distribution config and starting out
of rebar_prv_shell and into rebar_dist_utils. The module is able to
handle standard config options and boot a distributed node mode. This
could be used in plugins (once it is exposed) and other providers like
CT.

Configuration is also expanded so that options like:

    {dist, [{sname, atom()}, {name, atom()}, {setcookie, term()}]}

can be used and will be handled as a default. The config handler
supports similar terms from the command line being parsed in if the
calling provider supports them.

A test suite is added for configuration handling.

Unsure if this should be a final supported format or if we should
support other ways to match instead.

This is a demo to solve the issue hilighted in
https://github.com/erlang/rebar3/pull/1072

By default, the dependency only handled versioned packages and top-level
source dependencies, and locks were being ignored.

This patch makes it so locks and package deps are being considered,
generating full-blown path lists.

Should fix #1117

Following suggestions from @psyeugenic, this code terminates and waits
for the termination of the port handling IO before booting our own,
which should get rid of annoying warnings.

We also allow for the failure to shutdown the user worker under
kernel_sup, since it is likely not there anymore in many scenarios,
preventing crashes.

Allows overwrite the default cache directory using the environment
variable REBAR_CACHE_DIR.