Do not use set -e in helper shell scripts

It is not a substitute for proper error checking, it can easily cause
more trouble than good and it would be a burden for contributors and a
source for potential misbehavior. See this take on the topic for
example: http://mywiki.wooledge.org/BashFAQ/105

shell-completion/parse-commands.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # Parse hledger's help and output all commands and command aliases in
 # parenthesis. Do not output single letter command aliases, it's not useful.
-set -euo pipefail
+set -uo pipefail
 
 declare commands_help
 commands_help=$(hledger)

shell-completion/parse-options.sh

@@ -2,7 +2,7 @@
 # Parse hledger's help and output long options. Do not propose single letter
 # completions. Options requiring an argument make that explicit by appending the
 # equal sign (=)
-set -euo pipefail
+set -uo pipefail
 
 declare subcommand=${1:-}
 declare hledgerArgs=(--help)