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#!/bin/sh
# hstow -- POSIX sh minimal reimplementation of GNU Stow for dotfiles
#
# Copyright (C) 2022-2023 Sean Whitton <spwhitton@spwhitton.name>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# The point of this script is to obtain minimally functional dotfiles
# handling in one's home directory on even machines that lack a Perl
# interpreter. As such, many of GNU Stow's more advanced features are
# not reimplemented. Git depends on Perl, for now, but my two methods
# for deploying my dotfiles to remote machines -- my INSINUATE-DOTFILES
# Consfigurator property and 'insinuate-dotfiles' shell script -- do not
# depend on having Git on the remote side. See also 'bstraph' script.
#
# We completely skip filenames containing control characters, including
# newline and tab, as POSIX find(1) lacks -print0, and it's unlikely
# you'd need to stow any such files.
# Technique from <https://dwheeler.com/essays/filenames-in-shell.html>.
set -efu
IFS="$(printf '\n\t')"
export LC_ALL=C
tab="$(printf '\t')"
cchars="$(printf '*[\001-\037\177]*')"
if ! command -v readlink >/dev/null; then
readlink () {
# Safe parse of ls(1) output given its POSIX specification.
#
# We want the ninth field onwards in awk's sense --
# i.e. collapsing multiple runs of blanks between the first nine
# fields -- but we mustn't collapse blanks from there onwards.
n=$((3 + $(echo "$1" | wc -m)))
ls -ld "$1" \
| sed -E \
"s/^[[:blank:]]*([^[:blank:]]+[[:blank:]]+){8}.{$n}//"
}
fi
# Here we unconditionally bypass readlink(1), for speed.
# The long regexp is because only BREs have backreferences in POSIX.
readlinks () {
while read -r line; do
printf '%s\t%s\n' "$line" "$(ls -ld "$line")"
done | sed \
's/\([^\t]*\)\t\([^[:blank:]]\{1,\}[[:blank:]]\{1,\}\)\{8\}\1 -> /\1\t/'
}
disjoin_hstow_file () {
if [ -e "$DIR/$1" ]; then
while read -r line; do
[ -n "$line" ] && printf "|$2" "$line"
done <"$DIR/$1" | cut -c2-
fi
}
dir_contents () {
( cd "$1"; find . ! -name . ! -name "$cchars" -print -prune )
}
fail () {
echo >&2 "hstow: $*"
exit 127
}
usage () {
fail "usage: hstow stow|unstow|restow|adopt DIRECTORY"
}
stow () {
cd "$DIR"
[ -d "$HOME/.STOW" ] || mkdir "$HOME/.STOW"
[ -f "$HOME/.STOW/.stow" ] || touch "$HOME/.STOW/.stow"
[ -h "$HOME/.STOW/$NAME" ] \
|| ( cd "$HOME/.STOW"; ln -s "$DIR" "$NAME" )
conflicts=
ignores="$(disjoin_hstow_file .hstow-local-ignore "./%s")"
# Files that (i) always/often have their symlinks replaced with
# regular files when applications access them; and (ii) we don't
# ever want to edit the copy under $DIR directly, but only via the
# link/copy under $HOME.
$always_adopt \
|| adoptions="$(disjoin_hstow_file .hstow-always-adopt "./%s")"
for file in $(find . ! -name . ! -type d ! -name "$cchars" \
! -name .gitignore \
! -name .hstow-local-ignore \
! -name .hstow-always-adopt \
! -name .hstow-unstow-ignore \
| grep -v '^\./\.git/'); do
file_dir="$(dirname $file)"
if [ -n "$ignores" ]; then
eval case "'$file'" in "${ignores})" continue ";;" esac
eval case "'$file_dir'" in "${ignores})" continue ";;" esac
fi
rel="$(echo $file|sed -E 's#/dot[-.]([^/]+)#/.\1#g; s#^\./##')"
dotdotslashes="$(echo $rel|sed -E 's#[^/]*$##; s#[^/]+#..#g')"
target="${dotdotslashes}.STOW/$NAME/$rel"
link="$HOME/$rel"
link_target=
[ -h "$link" ] && link_target="$(readlink $link)"
[ "$target" = "$link_target" ] && continue
if [ ! -h "$link" -a ! -h "$file" -a -f "$link" ]; then
if $always_adopt \
|| ( [ -n "$adoptions" ] \
&& eval case "'$file'" in \
"${adoptions})" exit 0 ";;" \
"*)" exit 1 ";;" \
esac ); then
mv -f "$link" "$file"
ln -s "$target" "$link"
else
conflicts="$conflicts${tab}$file"
fi
elif [ -h "$link" ]; then
# With at least GNU ln(1), passing -f, but not also -T, does
# not replace an existing link in some cases.
# -T is not POSIX, so we remove any existing link first.
rm "$link"
ln -s "$target" "$link"
else
mkdir -p "$HOME/$file_dir"
ln -s "$target" "$link"
fi
done
[ -z "$conflicts" ] && return
echo >&2 "hstow: encountered conflicts:"
for conflict in $conflicts; do echo >&2 " $conflict"; done
exit 127
}
unstow () {
cd "$HOME"
# For speed, skip directories into which we'll never stow anything.
ignores="$(disjoin_hstow_file .hstow-unstow-ignore "./%s/")"
dir_pat=".$(echo $DIR | cut -c$(echo $HOME | wc -m | tr -d ' ')-)/"
dirs_pat="$(echo "^($dir_pat|$ignores)" | sed -e 's#\.#\\.#g')"
for file in \
$(find . ! \( -user "$(id -un)" -o -group "$(id -gn)" \) \
-prune -o -type l ! -name . ! -name "$cchars" -print \
| grep -Ev "$dirs_pat" | readlinks | awk -F'\t' \
'$2 ~ /^(\.\.\/)*\.STOW\/'"$NAME"'\// { print $1 }'); do
rm "$file"
while true; do
file="$(dirname $file)"
[ "$file" = . ] && break
if [ -z "$(dir_contents $file)" ]; then
rmdir "$file"
else
break
fi
done
done
[ -e "$HOME/.STOW/$NAME" ] && rm "$HOME/.STOW/$NAME"
if [ -d "$HOME/.STOW" ] \
&& [ "$(dir_contents $HOME/.STOW)" = "./.stow" ]; then
rm "$HOME/.STOW/.stow"
rmdir "$HOME/.STOW"
fi
}
[ $# = 2 ] || usage
[ -d "$2" ] || fail "$2 is not an existing directory"
DIR="$(cd $2; pwd)"
[ "$(echo $DIR | cut -c-$(($(echo $HOME | wc -m) - 1)))" = "$HOME" ] \
|| fail "$DIR is not below $HOME"
NAME="$(echo $DIR | tr / _)"
always_adopt=false
case "$1" in
'stow') stow ;;
'unstow') unstow ;;
'restow') unstow; stow ;;
'adopt') always_adopt=true; stow ;;
*) usage ;;
esac
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