Minimum bash versions

4.2

• more robust test suite: completion-display-width 0 in inputrc
• code cleanups: negative array indexes (but not assignments); suspect grep: [${#
• code cleanups: test/[[ -v
• TBD: lastpipe option

LTS OS versions with bash 4.1:

• CentOS 6 etc, EoL 2020-11-30

4.3

• code cleanups, major niceties: namerefs
• code cleanups: negative array index assignments, unsetting; suspect grep: [${#
• code cleanups: no longer need some array nounset defense like in (($[#COMPREPLY[@]})) && COMPREPLY=("${COMPREPLY[@]/%/ }")

LTS OS versions with bash 4.2:

• RHEL and CentOS 7, EoL 2024-06-30 (ELS 2026-06-30)

4.4

• code cleanups: parameter transformations (e.g. ${foo@Q})

Will likely skip this directly to 5.0 though; see 4.2 LTS OS's.

LTS OS versions with bash 4.3:

• Debian 8, EoL 2020-06-30
• Ubuntu 14.04, EoL 2024-04
• Ubuntu 16.04, EoL 2026-04

5.0

TBD

LTS OS versions with bash 4.4:

• RHEL 8 and derivatives, EoL 2029-05-31
• Debian 9, EoL 2022-06-30
• Ubuntu 18.04, EoL 2028-04