Paths for --filename and <file> are not resolved correctly

The --filename command line argument cannot be given absolute paths or relative paths that start at the current directory or a parent directory. The same goes for the -f alias and for <file> in a config file.

Given the following directory structure:

├── CURRENT_DIR
│   ├── subdir
│   │   └── Test.php
│   └── Test.php
└── other
    └── Test.php

Actual Behavior

Running phpdoc from CURRENT_DIR may or may not find the file "Test.php" using the command line phpdoc parse --filename path --force -vvv. I get the following results for different paths:

• Test.php - found
• ./Test.php - not found
• ../CURRENT_DIR/Test.php - not found
• subdir/Test.php - found
• subdir/../Test.php - not found
• ./subdir/Test.php - not found
• ../other/Test.php - not found
• /abs/path/to/other/Test.php - not found

The debug output is

[2018-12-23 17:19:32] app.INFO: One of the project's settings have changed, forcing a complete rebuild [] []
[2018-12-23 17:19:32] app.INFO: Elapsed time to parse all files: 0s [] []
[2018-12-23 17:19:32] app.INFO: Peak memory usage: 10M [] []

Expected Behavior

A "Test.php" file should be found in all of these paths.

Steps to Reproduce the Problem

• $ mkdir -p dirtest/CURRENT_DIR/subdir dirtest/other
• $ cd dirtest/CURRENT_DIR
• $ touch Test.php
• $ cp Test.php subdir
• $ cp Test.php ../other
• $ phpdoc parse --filename ../other/Test.php --force -vvv

Your environment

• Version used: v3.0.x-dev@ee92b8f
• Install method: cloned "develop" branch
• php version: 7.2.10
• Operating system and version: Kubuntu 18.04

Start at the phpdoc parse command and trace handling for --filename, its -f alias, and <file> values from a config file. Reproduce the listed paths from CURRENT_DIR, then verify that absolute paths, parent-directory paths, and paths containing ./ or .. all locate the expected files.