ISC bind-utils dig completion with hints helper option file for "@"

[mave007]

Summary

Adding dedicated completion for ISC BIND dig (completions-core/dig.bash), registers it in the build, adds tests, and removes dig from the generic _comp_complete_known_hosts registration in bash_completion so installed
dig.bash can take effect instead of always completing only hostnames.

Behavior (completions-core/dig.bash)

• Switch-style dig: query CLASS, RRTYPE, and NAME may appear in any order, plus +query options and @server
• One class and one type for completion purposes: after each is set (bare or via -c /-t flags) completion stops offering more classes or types. Meanwhile + options can be multiple.
• Bare ANY: classified as RRTYPE first (matches dig <NAME> ANY);
• CHAOS + TXT: suggests fixed *.bind-style names when class is CH and type is TXT.
• Query names: -q, dotted tokens, or non–class/type-prefix tokens use _comp_compgen_known_hosts where applicable.
• compopt +o bashdefault +o default to avoid broad default hostname fallback on empty COMPREPLY.
• @server: ~/.ssh/known_hosts, or BASH_COMPLETION_CMD_DIG_NS_HINTS_FILE for suffix-based hints (longest pattern wins, * defaults; trailing dots on name/pattern normalized). Format documented in comments

Example of $BASH_COMPLETION_CMD_DIG_NS_HINTS_FILE:

# Declare this in `.bashrc` as:
# export BASH_COMPLETION_CMD_DIG_NS_HINTS_FILE=<full_path_to_this_file>

# Glob useful to declare resolvers. Will match always as auto-completion
* 1.1.1.1 8.8.8.8 9.9.9.9 127.0.0.53

# Root zone and COM name servers
. a.root-servers.net. b.root-servers.net. c.root-servers.net. d.root-servers.net. e.root-servers.net. f.root-servers.net. g.root-servers.net. h.root-servers.net. i.root-servers.net. j.root-servers.net. k.root-servers.net. l.root-servers.net. m.root-servers.net.
com a.gtld-servers.net. b.gtld-servers.net. c.gtld-servers.net. d.gtld-servers.net. e.gtld-servers.net. f.gtld-servers.net. g.gtld-servers.net. h.gtld-servers.net. i.gtld-servers.net. j.gtld-servers.net. k.gtld-servers.net. l.gtld-servers.net. m.gtld-servers.net.

# Internal usage
internal.example.com 192.0.2.1 198.51.100.2 203.0.113.3

Note on removing dig from ./bash_completion

Given that dig was registered with _comp_complete_known_hosts, that generic hostname completer took precedence over the lazy-loaded completions-core/dig.bash, so dedicated completion for class, RR type, @server, and + options never ran.

The other option to avoid this case is to add into .bashrc or .bash_profile the load of the dig completion after loading bash-completion with _comp_load (example in macos with brew installation):

[[ -r "${BREWPREFIX:-/opt/homebrew}/etc/profile.d/bash_completion.sh" ]] && . "${BREWPREFIX:-/opt/homebrew}/etc/profile.d/bash_completion.sh"
_comp_load dig 2>/dev/null

Files

File	Change
completions-core/dig.bash	New dig completion
completions-core/Makefile.am	Install dig.bash
bash_completion	Stop registering dig with _comp_complete_known_hosts
test/t/test_dig.py	Integration tests
test/t/Makefile.am	Register test_dig.py

Testing

• pytest test/t/test_dig.py (cases with require_cmd=True need dig on PATH).