Add environment and auto-completion for "iceowl" host (macOS support)

This commit adds a new environment configuration (1) for the new
`iceowl` host. The auto-completion scripts bundled with the Homebrew
git (2) and bash (3) forumlas should also be imported.

References:

  (1) https://github.com/arcticicestudio/igloo/tree/83bbc2530dbb21f7e734aaa9e33898d7c4c67d50/snowblocks/bash/config/env
  (2) https://formulae.brew.sh/formula/git
  (3) https://formulae.brew.sh/formula/bash

Epic: GH-131
Closes GH-146

snowblocks/bash/bootstrap

@@ -127,9 +127,16 @@ __snowblock_bash::load_core_modules aliases functions prompt shelloptions
 # + Third-Party Scripts +
 # +---------------------+
 # Git prompt bash support.
+# Linux
 __snowblock_bash::load_third_party_scripts /usr/share/git/completion/git-prompt.sh
+# macOS
+__snowblock_bash::load_third_party_scripts /usr/local/opt/git/etc/bash_completion.d/git-prompt.sh
+
 # Programmable bash completion features.
+# Linux
 __snowblock_bash::load_third_party_scripts /usr/share/bash-completion/bash_completion
+# macOS
+__snowblock_bash::load_third_party_scripts /usr/local/opt/bash-completion@2/share/bash-completion/bash_completion
 
 __snowblock_bash::setup_history
 __snowblock_bash::register_binaries

snowblocks/bash/config/env/iceowl

@@ -0,0 +1,63 @@
+#!/usr/bin/env bash
+
+# Copyright (C) 2016-present Arctic Ice Studio <development@arcticicestudio.com>
+# Copyright (C) 2016-present Sven Greb <development@svengreb.de>
+
+# Project:    igloo
+# Repository: https://github.com/arcticicestudio/igloo
+# License:    MIT
+
+# This environment comnfiguration contains some hardcoded paths (/usr/local/opt) because "$(brew --prefix <package>)"
+# increases the start up time to more than 10 seconds!
+# It seems like for each execution of the Ruby code a new instance is spawned that also spawns more shell processes.
+# This might be caused by some macOS changes of essential logics from "El Capitan" to "High Sierra". Using the Homebrew
+# command in subshell calls works fine on "El Capitan" and older versions.
+
+export LANG=en_US.UTF-8
+export LC_MESSAGES=POSIX
+
+export EDITOR="$(command -v vim)"
+export MANPAGER="$(command -v less)"
+export VISUAL="$(command -v vim)"
+
+BREW_PATH_COREUTILS="/usr/local/opt/coreutils/libexec/gnubin"
+BREW_PATH_E2FSPROGS="/usr/local/opt/e2fsprogs/bin:/usr/local/opt/e2fsprogs/sbin"
+BREW_PATH_ICU4C="/usr/local/opt/icu4c/bin:/usr/local/opt/icu4c/sbin"
+BREW_PATH_OPENVPN="/usr/local/opt/openvpn/sbin"
+BREW_PATH_PYTHON="/usr/local/opt/python/libexec/bin"
+BREW_PATH_SQLITE="/usr/local/opt/sqlite/bin"
+
+BREW_MANPATH_BASE="/usr/local/share/man"
+BREW_MANPATH_COREUTILS="/usr/local/opt/coreutils/libexec/gnuman"
+
+BREW_INFOPATH_BASE="/usr/local/share/info"
+
+PATH_BIN="~/.bin"
+PATH_GIT_CONTRIB_DIFF_HIGHLIGHT="/usr/local/opt/git/share/git-core/contrib/diff-highlight"
+
+PATHS=(
+  "$BREW_PATH_COREUTILS"
+  "$BREW_PATH_E2FSPROGS"
+  "$BREW_PATH_ICU4C"
+  "$BREW_PATH_OPENVPN"
+  "$BREW_PATH_PYTHON"
+  "$BREW_PATH_SQLITE"
+  "$PATH_BIN"
+  "$PATH_GIT_CONTRIB_DIFF_HIGHLIGHT"
+  "$PATH"
+)
+
+MANPATHS=(
+  "$BREW_MANPATH_BASE"
+  "$BREW_MANPATH_COREUTILS"
+  "$MANPATH"
+)
+
+INFOPATHS=(
+  "$BREW_INFOPATH_BASE"
+  "$INFOPATH"
+)
+
+export PATH=$(IFS=$":"; echo "${PATHS[*]}")
+export MANPATH=$(IFS=$":"; echo "${MANPATHS[*]}")
+export INFOPATH=$(IFS=$":"; echo "${INFOPATHS[*]}")