`shellQuote` handles backslashes incorrectly

# "\\n" is needed here because Go templates interpret escapes in strings,
# shellQuote receives a single backslash here, without doubling it would receive a literal newline.
$ chezmoi execute-template '{{ shellQuote "\\n" }}'
'\\n'

$ chezmoi execute-template '{{ shellQuote "\\n" }}'
'\n'

RESULT   CHECK                       MESSAGE
ok       version                     v2.72.0, commit f81cb321789aa3df62871248f5e4d361a59e7cc1, built at 2026-08-03T00:00:00Z, built by Fedora
ok       latest-version              v2.72.0
ok       os-arch                     linux/amd64 (Fedora Linux 44 (Sway))
ok       build-info                  -tags=rpm_crashtraceback,noupgrade, CGO_ENABLED=1, GOEXPERIMENT=nodwarf5, GOAMD64=v1
ok       uname                       Linux mk 7.1.8-200.fc44.x86_64 #1 SMP PREEMPT_DYNAMIC Mon Aug 10 03:35:23 UTC 2026 x86_64 GNU/Linux
ok       go-version                  go1.26.5-X:nodwarf5 (gc)
ok       executable                  /usr/bin/chezmoi
ok       config-file                 found ~/.config/chezmoi/chezmoi.toml, last modified 2026-07-25T21:05:04+02:00
ok       source-dir                  ~/.local/share/chezmoi is a git working tree (clean)
ok       suspicious-entries          no suspicious entries
ok       working-tree                ~/.local/share/chezmoi is a git working tree (clean)
ok       dest-dir                    ~ is a directory
error    hardlink                    failed creating hardlink from ~/.local/share/chezmoi to /tmp: link ~/.local/share/chezmoi/.chezmoi-doctor-hardlink-test /tmp/chezmoi-doctor210992291/.chezmoi-doctor-hardlink-test: invalid cross-device link
ok       symlink                     created symlink from .new-name to .old-name
ok       umask                       022
ok       cd-command                  found /usr/bin/fish
ok       cd-args                     /usr/bin/fish
info     diff-command                not set
ok       edit-command                found /usr/bin/nvim
ok       edit-args                   /usr/bin/nvim
ok       git-command                 found /usr/bin/git, version 2.55.0
ok       merge-command               found /usr/bin/nvim
ok       shell-command               found /usr/bin/fish
ok       shell-args                  /usr/bin/fish
info     age-command                 age not found in $PATH
ok       gpg-command                 found /usr/bin/gpg, version 2.4.9
info     pinentry-command            not set
info     1password-command           op not found in $PATH
info     bitwarden-command           bw not found in $PATH
info     bitwarden-secrets-command   bws not found in $PATH
info     dashlane-command            dcli not found in $PATH
info     doppler-command             doppler not found in $PATH
info     gopass-command              gopass not found in $PATH
ok       keepassxc-command           found /usr/bin/keepassxc-cli, version 2.7.12
info     keepassxc-db                not set
info     keeper-command              keeper not found in $PATH
info     lastpass-command            lpass not found in $PATH
info     pass-command                pass not found in $PATH
info     passhole-command            ph not found in $PATH
info     protonpass-command          pass-cli not found in $PATH
info     rbw-command                 rbw not found in $PATH
info     vault-command               vault not found in $PATH
info     secret-command              not set