dist: Add vim syntax highlighting file

Closes #139.

dist/README.md

@@ -1,5 +1,8 @@
 # Distribution files for maddy
 
+**Disclaimer:** Most of the files here are maintained in a "best-effort" way.
+That is, they may break or become outdated from time to time. Caveat emptor.
+
 ## systemd unit
 
 `maddy.service` launches using default config path (/etc/maddy/maddy.conf).
@@ -26,3 +29,8 @@ See https://github.com/foxcpp/maddy/wiki/fail2ban-configuration for details.
 ## logrotate configuration
 
 Meant for logs rotation when logging to file is used.
+
+## vim ftdetect/ftplugin/syntax files
+
+Minimal supplement to make configuration files more readable and help you see
+typos in directive names.

dist/vim/ftdetect/maddy-conf.vim

@@ -0,0 +1 @@
+au BufNewFile,BufRead /etc/maddy/*,maddy.conf setf maddy-conf

dist/vim/ftplugin/maddy-conf.vim

@@ -0,0 +1,8 @@
+setlocal commentstring=#\ %s
+
+" That is convention for maddy configs. Period.
+"    - fox.cpp (maddy developer)
+setlocal expandtab
+setlocal tabstop=4
+setlocal softtabstop=4
+setlocal shiftwidth=4

dist/vim/syntax/maddy-conf.vim

@@ -0,0 +1,115 @@
+" vim: noexpandtab ts=4 sw=4
+
+if exists("b:current_syntax")
+	finish
+endif
+
+" Lexer-defined rules
+syn match		maddyComment	"#.*"
+syn region      maddyString		start=+"+ skip=+\\\\\|\\"+ end=+"+ oneline
+
+syn region		maddyBlock		start="{" end="}" transparent fold
+
+hi def link maddyComment	Comment
+hi def link maddyString		String
+
+" Parser-defined rules
+syn match		maddyMacroName	"[a-z0-9_]" contained containedin=maddyMacro
+syn match		maddyMacro      "$(.\{-})" contains=maddyMacroName
+
+syn match		maddyMacroDefSign "=" contained
+syn match		maddyMacroDef     "\^$([a-z0-9_]\{-})\s=\s.\+" contains=maddyMacro,maddyMacroDefSign
+
+hi def link maddyMacroName			Identifier
+hi def link maddyMacro				Special
+hi def link maddyMacroDefSign		Special
+
+" config.Map values
+syn keyword maddyBool yes no
+
+syn match maddyInt '\<\d\+\>'
+syn match maddyInt '\<[-+]\d\+\>'
+syn match maddyFloat '\<[-+]\d\+\.\d*\<'
+
+hi def link maddyBool		Boolean
+hi def link maddyInt		Number
+hi def link maddyFloat		Float
+
+" Module values
+
+" grep --no-file -E 'Register.*\(".+", ' **.go | sed -E 's/.+Register.*\("([^"]+)", .+/\1/' | sort -u
+syn keyword maddyModule
+	\ dummy
+	\ extauth
+	\ imap
+	\ pam
+	\ queue
+	\ remote
+	\ replace_rcpt
+	\ replace_sender
+	\ require_matching_ehlo
+	\ require_matching_rdns
+	\ require_mx_record
+	\ shadow
+	\ smtp
+	\ sql
+	\ submission
+	\ test_check
+	\ test_modifier
+	\ verify_dkim
+
+syn keyword maddyDispatchDir
+	\ check
+	\ modify
+	\ default_source
+	\ source
+	\ default_destination
+	\ destination
+	\ reject
+	\ deliver_to
+
+" grep --no-file -E 'cfg..+\(".+", ' **.go | sed -E 's/.+cfg..+\("([^"]+)", .+/\1/' | sort -u
+syn keyword maddyModDir
+	\ appendlimit
+	\ auth
+	\ auth_domains
+	\ auth_perdomain
+	\ autogenerated_msg_domain
+	\ bounce
+	\ broken_sig_action
+	\ debug
+	\ defer_sender_reject
+	\ driver
+	\ dsn
+	\ fail_action
+	\ fsstore
+	\ helper
+	\ hostname
+	\ insecure_auth
+	\ io_debug
+	\ junk_mailbox
+	\ location
+	\ max_message_size
+	\ max_parallelism
+	\ max_recipients
+	\ max_tries
+	\ mtasts_cache
+	\ no_sig_action
+	\ read_timeout
+	\ require_tls
+	\ sqlite3_busy_timeout
+	\ sqlite3_cache_size
+	\ sqlite3_exclusive_lock
+	\ storage
+	\ storage_perdomain
+	\ submission
+	\ target
+	\ tls
+	\ use_helper
+	\ write_timeout
+
+hi def link maddyModDir		Identifier
+hi def link maddyModule		Identifier
+hi def link maddyDispatchDir		Identifier
+
+let b:current_syntax = "maddy"