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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
. ~/src/dotfiles/lib-src/posix-defuns.sh
# readlink(1) is not POSIX, so we require an alternative.
# For simplicity, always use this even if readlink(1) is installed.
readlinks () {
local restc=$1 assume="${2:-false}" first= rest=
local fields_temp="$(mkstemp)" targets_temp="$(mkstemp)"
# This first pipeline involves a safe parse of ls(1) output given
# its POSIX specification.
# We want the ninth field onwards in the output of ls(1) in awk's
# sense -- i.e. collapsing runs of multiple blanks between the first
# nine fields -- but we mustn't collapse blanks from there onwards.
exec 3>&1
while read -r first rest; do
[ -n "$rest" ] && rest="$tab$rest"
if $assume || [ -h "$first" ]; then
echo "$first"
echo "$first$rest" >>"$fields_temp"
else
echo "$first$rest" >&3
fi
done \
| awk '{ gsub(/"/, "\"'"'"'\"'"'"'\"")
printf "\"%s\"\n", $0 }' | xargs -E '' -- ls -ld \
| sed -E 's/^([^[:blank:]]+[[:blank:]]+){8}//; /^\.$/d' \
| sort -o "$targets_temp" # undo how ls(1) sorts non-dirs first
sort -t"$tab" -k1 -o "$fields_temp" "$fields_temp"
if [ "$(wc -l <"$fields_temp")" \
-ne "$(wc -l <"$targets_temp")" ]; then
rm "$fields_temp" "$targets_temp"
fail "line counts unequal; are there newlines in link targets?"
fi
# Only BREs have backreferences in POSIX.
paste "$fields_temp" "$targets_temp" \
| sed 's/^\([^\t]\{1,\}\)\t\('\
"$(printf "%${restc}s" | sed 's/ /[^\\t]\\{1,\\}\\t/g')"\
'\)\1 -> /\1\t\2/' \
| awk -F'\t' 'NF == '$((2+$restc))' && $NF !~ /[\001-\037\177]/'
rm "$fields_temp" "$targets_temp"
}
disjoin_file () {
while read -r line; do
[ -n "$line" ] && printf "|$2" "$line"
done <"$DIR/$1" | sed 's#^.##; s#/#\\/#g'
}
globs_to_find_args () {
local file="$DIR/$1"; shift
printf '%s\n' "$@" | cat - $([ -e "$file" ] && echo "$file") \
| awk -F'\n' -vOFS='\t' \
'/\/\*$/ { sub(/..$/, ""); prune[++c] = "./" $0; next }
$0 { notpath[++d] = "./" $0 }
# We want to prevent find(1) recursing into directories
# of these names, but not prevent the remainder of the
# find(1) expression from matching the names themselves.
# This is what is correct for globs of the form "dir/*".
# While it is true that neither of the find(1) commands
# which use globs_to_find_args() match directories, such
# that it would not make sense to add a line to one of
# .hstow-*-ignore with the aim of excluding the contents
# of a directory but not the directory itself, it could
# be that the name is currently a symlink that we should
# unstow. (Also note that we do not pass -L to find(1),
# so we will not recurse into symlinks to dirs anyway.)
END { if (c) {
print "(", "(", "-path", prune[1]
for (i = 2; i <= c; i++)
print "-o", "-path", prune[i]
print ")", "-prune", "-o", "-name", "*", ")"
}
for (j in notpath) print "!", "-path", notpath[j]
}'
}
usage () {
fail "usage: hstow stow|unstow|restow|adopt DIRECTORY"
}
stow () {
cd "$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" "$NAME" )
conflicts="$(stow1)"
[ -z "$conflicts" ] && return
echo >&2 "hstow: encountered conflicts:"
for conflict in $conflicts; do echo >&2 " $conflict"; done
exit 127
}
stow1 () {
if $always_adopt; then
adoptp=1
elif ! [ -e .hstow-always-adopt ]; then
adoptp=0
else
# EREs matching 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 $HOME.
# We might list globs in this file & convert them to EREs here.
adoptp="$(printf 'rel ~ /^(%s)/' \
"$(disjoin_file .hstow-always-adopt "%s")")"
fi
find . $(globs_to_find_args .hstow-local-ignore ".git/*") \
! -name . ! -type d ! -name "$cchars" ! -name .gitignore \
! -name .hstow-local-ignore ! -name .hstow-always-adopt \
! -name .hstow-unstow-ignore -print \
| awk -F'\n' -vOFS='\t' '
{ rel = $1; gsub(/\/dot[-.]/, "/.", rel); gsub(/^\.\//, "", rel)
dotdotslashes = rel
sub(/[^\/]*$/, "", dotdotslashes)
gsub(/[^\/]+/, "..", dotdotslashes)
$2 = $1
$3 = $1; sub(/\/[^/]+$/, "", $3)
$1 = ENVIRON["HOME"] "/" rel
$4 = '"$adoptp"' ? "true" : "false"
$5 = dotdotslashes ".STOW/'"$NAME"'/" rel
print
}' | readlinks 4 \
| while read -r link file file_dir adopt target link_target; do
if [ "$target" = "$link_target" ]; then
continue
elif [ -n "$link_target" ]; then # implies $link is a symlink
# With at least GNU ln(1), passing -f, but not also -T, does
# not replace an existing link in some cases.
# -T is not POSIX, so we remove any existing link first.
rm "$link"
ln -s "$target" "$link"
elif $adopt && [ ! -h "$file" -a -f "$link" ]; then
mv -f "$link" "$file"
ln -s "$target" "$link"
elif [ -d "$link" ] && rmdir "$link" 2>/dev/null; then
ln -s "$target" "$link"
elif [ -e "$link" ]; then
echo "$file" # into $conflicts
else
mkdir -p "$HOME/$file_dir"
ln -s "$target" "$link"
fi
done
}
unstow () {
cd "$HOME"
# .hstow-unstow-ignore is a list of globs matching dirs into which
# we'll never stow anything. We have this for the sake of speed.
#
# awk's close() calls pclose(3), completing all the link deletions.
# POSIX.1 "Utility Description Defaults", "Consequences of Errors"
# implies that should rmdir(1) encounter a non-empty directory, it
# should proceed to attempt to remove the next operand.
# Thus, here, -p means that we do not need to sort the operands.
# We don't know the code with which rmdir(1) will exit, and if it is
# 255 then xargs will give up. So we wrap in a call to sh -c.
find . ! \( -user "$(id -un)" -o -group "$(id -gn)" \) -prune -o \
$(globs_to_find_args \
.hstow-unstow-ignore ".STOW/*" \
"$(echo "$DIR" \
| cut -c$((1 + $(echo "$HOME" | wc -m)))-)/*") \
-type l ! -name . ! -name "$cchars" -print \
| readlinks 0 true \
| awk -F'\t' -vOFS='\t' '$2 ~ /^(\.\.\/)*\.STOW\/'"$NAME"'\// \
{ gsub(/"/, "\"'"'"'\"'"'"'\"", $1)
printf "\"%s\"\n", $1 | "xargs -E '' -- rm -f"
sub(/^.\//, "", $1)
sub(/\/?[^/]+$/, "", $1)
if ($1) dirs[++i] = $1
} END { close("xargs -E '' -- rm -f")
for (d in dirs) printf "\"%s\"\n", dirs[d]
}' | xargs -E '' -- sh -c 'rmdir -p -- "$@" 2>/dev/null ||:' --
[ -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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